Track system for traction of an off-road vehicle such as a snowmobile or an all-terrain vehicle (atv)

ABSTRACT

A track system for traction of an off-road vehicle such as a snowmobile or an all-terrain vehicle (ATV). The track system comprises a track-engaging assembly and a track disposed around the track-engaging assembly. The track system may be configured to have a reduced noise profile so as to generate less noise, enhanced track rigidity characteristics to improve its traction and floatation, and/or other features improving use and performance of the off-road vehicle.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 13/689,128, filed on Nov. 29, 2012,which claims the benefit under 35 USC 119(e) of U.S. Provisional PatentApplication 61/564,630, filed on Nov. 29, 2011 and hereby incorporatedby reference herein.

FIELD OF THE INVENTION

The invention relates generally to off-road vehicles such as snowmobilesand all-terrain vehicles (ATV) and, more particularly, to track systemsfor traction of snowmobiles, ATVs and other off-road vehicles.

BACKGROUND

Snowmobiles allow efficient travel on snowy and in some cases icygrounds. A snowmobile comprises a track system which engages the groundto provide traction. The track system comprises a track-engagingassembly and an endless track that moves around the track-engagingassembly and engages the ground to generate traction. The endless tracktypically comprises an elastomeric body in which are embedded certainreinforcements, such as transversal stiffening rods providingtransversal rigidity to the track, longitudinal cables providingtensional strength, and/or fabric layers. The track-engaging assemblycomprises wheels and in some cases slide rails around which the endlesstrack is driven.

Various considerations are important when it comes to a snowmobile's useand performance.

For example, a snowmobile generates noise, including noise generated byits track system. Various factors may contribute to the noise generatedby the snowmobile's track system. For instance, in some cases: impactsbetween roller and/or other wheels of the track-engaging assembly andthe transversal stiffening rods of the endless track; impacts betweenthe slide rails and the transversal stiffening rods of the endlesstrack; impacts between the slide rails and slide members (e.g., “clips”)of the endless track, if any; impacts between the ground and tractionprojections of a ground-engaging outer side of the endless track; andcontact between the endless track and drive wheels of the track-engagingassembly may contribute to the noise generated by the snowmobile's tracksystem.

As another example, traction and floatation provided by a snowmobile'strack system depend on rigidity of the track system's endless track.While longitudinal flexibility of the track is desirable in order toefficiently drive the track around the track-engaging assembly,transversal rigidity of the track is desirable in order to have a properground-contacting area for traction and floatation.

Similar considerations may be important for all-terrain vehicles (ATVs)equipped with track systems having endless tracks providing traction tothe ATVs on the ground (e.g., an ATV equipped with two front tracksystems in place of two front wheels and two rear track systems in placeof two rear wheels) and/or for other types of off-road vehicles.

While certain developments have been made to improve performance oftrack systems of snowmobiles, ATVs and other off-road vehicles, thereremains a need for improvements in such track systems.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, there is provided a trackfor traction of an off-road vehicle. The track is mountable around atrack-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods has a cross-sectionperpendicular to a longitudinal axis of the stiffening rod. Thecross-section of the stiffening rod is elongate.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods has a cross-sectionperpendicular to a longitudinal axis of the stiffening rod. Thecross-section of the stiffening rod has an aspect ratio of at least 4.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods has a cross-sectionperpendicular to a longitudinal axis of the stiffening rod. A ratio of(i) a thickness of the cross-section of the stiffening rod in athickness direction of the track over (ii) a thickness of a carcass ofthe track from the inner surface to the ground-engaging outer surface inthe thickness direction of the track is less than 0.7.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods has a cross-sectionperpendicular to a longitudinal axis of the stiffening rod. A thicknessof the cross-section of the stiffening rod in a thickness direction ofthe track is less than 3.5 mm.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track is free of reinforcing fabric between the innersurface and the ground-engaging outer surface along at least part of alength of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track is free of reinforcing fabric.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. A thickness of the track from the inner surface to theground-engaging outer surface is no more than 0.25 inches. The track isfree of reinforcing fabric between the inner surface and theground-engaging outer surface along at least part of a length of thetrack.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods comprises a cavity.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The inner surfacecomprises an idler wheel path for the idler wheel. The track alsocomprises a plurality of stiffening rods extending transversally to alongitudinal direction of the track. Each stiffening rod of theplurality of stiffening rods comprises a recess aligned with the idlerwheel path.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods is shaped such that athickness of elastomeric material between (i) the inner surface and (ii)a surface of the stiffening rod facing the inner surface varies in thelongitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Eachstiffening rod of the plurality of stiffening rods is dimensioned suchthat the stiffening rod does not extend beneath laterally-outmosttrack-contacting devices of the track-engaging assembly.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Afirst one of the stiffening rods and a second one of the stiffening rodsbeing stacked in a thickness direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Agiven one of the stiffening rods is located between adjacent ones of thetraction projections in the longitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Afirst one of the stiffening rods is different from a second one of thestiffening rods that succeeds the first one of the stiffening rods inthe longitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Theplurality of stiffening rods includes an elastomeric fiber-reinforcedrod.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner side for facing the track-engaging assembly and aground-engaging outer side for engaging the ground. The ground-engagingouter side comprises a ground-engaging outer surface and a plurality oftraction projections projecting from the ground-engaging outer surface.Elastomeric material of the ground-engaging outer side is different fromelastomeric material between the inner side and the ground-engagingouter side such that at least one of: a hardness of the elastomericmaterial of the ground-engaging outer side is lower than a hardness ofthe elastomeric material between the inner side and the ground-engagingouter side; and a modulus of elasticity of the elastomeric material ofthe ground-engaging outer side is lower than a modulus of elasticity ofthe elastomeric material between the inner side and the ground-engagingouter side.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The inner surfacecomprises an idler wheel path for the idler wheel. A shock absorbency ofthe track at a widthwise position of the idler wheel path is greaterthan a shock absorbency of the track at a widthwise position outside theidler wheel path.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. Elastomeric materialat a widthwise position of the idler wheel path is different fromelastomeric material at a widthwise position outside the idler wheelpath such that at least one of: a hardness of the elastomeric materialat the widthwise position of the idler wheel path is lower than ahardness of the elastomeric material at the widthwise position outsidethe idler wheel path; and a modulus of elasticity of the elastomericmaterial at the widthwise position of the idler wheel path is lower thana modulus of elasticity of the elastomeric material at the widthwiseposition outside the idler wheel path.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a layer of stiffening cables extendingtransversally to a longitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track also comprises a plurality of stiffening rodsextending transversally to a longitudinal direction of the track. Thetrack further comprises a layer of stiffening cables extendingtransversally to the longitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The ground-engagingouter surface defines an idler wheel path projection that is locatedbetween adjacent ones of the traction projections in a longitudinaldirection of the track and that is aligned with the idler wheel path ina widthwise direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. At least one of the inner surface and the ground-engaging outersurface comprises a plurality of longitudinal rigidifiers for impartinglongitudinal rigidity to the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The inner surfacecomprises an idler wheel path for the idler wheel. The idler wheel pathis uneven in a longitudinal direction of the track.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track is at least mainly made of fiber-reinforcedelastomeric material.

In accordance with another aspect of the invention, there is provided atrack for traction of an off-road vehicle. The track is mountable arounda track-engaging assembly of the off-road vehicle. The track-engagingassembly comprises a drive wheel for driving the track and an idlerwheel for contacting the track. The track is elastomeric to be flexiblearound the track-engaging assembly. The track comprises an inner surfacefor facing the track-engaging assembly, a ground-engaging outer surfacefor engaging the ground, and a plurality of traction projectionsprojecting from the ground-engaging outer surface. Cellular elastomericmaterial is located at a widthwise position of the idler wheel path.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises: an inner surface for facing the track-engaging assembly, theinner surface comprising an idler wheel path; a ground-engaging outersurface for engaging the ground; and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The track-engagingassembly comprises a drive wheel for driving the track and a pluralityof idler wheels for contacting the track. The plurality of idler wheelsincludes a set of idler wheels spaced apart in a longitudinal directionof the track system and disposed to roll on the idler wheel path of thetrack. The set of idler wheels is arranged such that a longitudinalspacing of any two successive idler wheels of the set of idler wheels isless than half of a length of the track system.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises: an inner surface for facing the track-engaging assembly, theinner surface comprising an idler wheel path; a ground-engaging outersurface for engaging the ground; and a plurality of traction projectionsprojecting from the ground-engaging outer surface. The track-engagingassembly comprises a drive wheel for driving the track and a pluralityof idler wheels for contacting the track. The plurality of idler wheelsincludes at least four idler wheels spaced apart in a longitudinaldirection of the track and disposed to roll on the idler wheel path ofthe track.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track-engaging assembly comprises a drive wheel for drivingthe track and a plurality of side rails spaced apart in a widthwisedirection of the track system to slide against a bottom run of thetrack. The plurality of side rails is arranged such that a widthwisespacing of any two adjacent slide rails of the plurality of side railsis less than half of a width of the track system.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track-engaging assembly comprises a drive wheel for drivingthe track and a plurality of side rails spaced apart in a widthwisedirection of the track system to slide against a bottom run of thetrack. The plurality of side rails includes at least three slide rails.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track-engaging assembly comprises a drive wheel for drivingthe track and an idler wheel for contacting a bottom run of the track.The track-engaging assembly also comprises a track tensioner formaintaining a tension of the track.

In accordance with another aspect of the invention, there is provided atrack-engaging assembly for a track system providing traction of anoff-road vehicle. The track-engaging assembly is configured to engage atrack disposed around the track-engaging assembly. The track iselastomeric to be flexible around the track-engaging assembly. The trackcomprises an inner surface for facing the track-engaging assembly, aground-engaging outer surface for engaging the ground, and a pluralityof traction projections projecting from the ground-engaging outersurface. The track-engaging assembly comprises a drive wheel for drivingthe track and an idler wheel for contacting a bottom run of the track.The track-engaging assembly also comprises a track tensioner formaintaining a tension of the track. The track tensioner comprises aresilient device for contacting a segment of a top run of the track.

These and other aspects of the invention will now become apparent tothose of ordinary skill in the art upon review of the followingdescription of embodiments of the invention in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of embodiments of the invention is providedbelow, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 shows an example of a snowmobile comprising a track system inaccordance with an embodiment of the invention;

FIG. 2 shows a perspective view of components of the track system;

FIG. 3 shows a perspective view of part of a track of the track system;

FIGS. 4 to 7A respectively show an elevation view, a plan view of aninner side, a longitudinal cross-sectional view, and a widthwisecross-sectional view of part of the track;

FIGS. 7B to 7D shows a widthwise cross-sectional view of part of thetrack according to other embodiments of the invention;

FIGS. 8 and 9 respectively show the track with and without a slidemember;

FIGS. 10 to 21 show different shapes of transversal stiffening rods ofthe track in accordance with various embodiments of the invention;

FIGS. 22A to 25 show different arrangements of transversal stiffeningrods of the track in accordance with various embodiments of theinvention;

FIG. 26 shows a reinforced elastomeric transversal stiffening rod inaccordance with an embodiment of the invention;

FIGS. 27 to 31 show zones of the track with different properties inaccordance with various embodiments of the invention;

FIGS. 32A to 32D show various embodiments of the track comprising alayer of transversal stiffening cables in accordance with variousembodiments of the invention;

FIGS. 33A and 33B show idler wheel path projections on a ground-engagingouter side of the track in accordance with an embodiment of theinvention;

FIGS. 34A and 34B show idler wheel path projections on a ground-engagingouter side of the track in accordance with another embodiment of theinvention;

FIG. 35 shows longitudinally uneven idler wheel paths on an inner sideof the track in accordance with an embodiment of the invention;

FIGS. 36 and 37 show different lengths of transversal stiffening rods ofthe track in accordance with various embodiments of the invention;

FIGS. 38 and 39 show longitudinal rigidifiers on an inner surface of acarcass of the track in accordance with an embodiment of the invention;

FIGS. 40 and 41 show different configurations of a suspension unit ofthe track system in accordance with various embodiments of theinvention;

FIGS. 42 and 43 show different examples of implementation of a tracktensioner of the track system in accordance with various embodiments ofthe invention;

FIG. 44 shows an example of implementation in which the track is atleast mainly made of fiber-reinforced elastomeric material in accordancewith an embodiment of the invention;

FIGS. 45A and 45B show an example of an all-terrain vehicle (ATV)comprising track systems in accordance with an embodiment of theinvention; and

FIGS. 46A and 46B show the ATV equipped with ground-engaging wheelsinstead of the track systems.

It is to be expressly understood that the description and drawings areonly for the purpose of illustrating certain embodiments of theinvention and are an aid for understanding. They are not intended to bea definition of the limits of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an example of a snowmobile 10 in accordance with anembodiment of the invention. The snowmobile 10 is designed fortravelling on snow and in some cases ice. In this embodiment, thesnowmobile 10 comprises a frame 11, a powertrain 12, a track system 14,a ski assembly 17, a seat 18, and a user interface 20, which enables auser to control the snowmobile 10.

The powertrain 12 is configured for generating motive power andtransmitting motive power to the track system 14 to propel thesnowmobile 10 on the ground. To that end, the powertrain 12 comprises aprime mover 15, which is a source of motive power that comprises one ormore motors (e.g., an internal combustion engine, an electric motor,etc.). For example, in this embodiment, the prime mover 15 comprises aninternal combustion engine. In other embodiments, the prime mover 15 maycomprise another type of motor (e.g., an electric motor) or acombination of different types of motor (e.g., an internal combustionengine and an electric motor). The prime mover 15 is in a drivingrelationship with the track system 14 That is, the powertrain 12transmits motive power from the primer mover 15 to the track system 14in order to drive (i.e., impart motion to) the track system 14.

The ski assembly 17 is turnable to allow steering of the snowmobile 10.In this embodiment, the ski assembly 17 comprises a pair of skis 191,192 connected to the frame 11 via a front suspension unit.

The seat 18 accommodates the user of the snowmobile 10. In this case,the seat 18 is a straddle seat and the snowmobile 10 is usable by asingle person such that the seat 18 accommodates only that persondriving the snowmobile 10. In other cases, the seat 18 may be anothertype of seat, and/or the snowmobile 10 may be usable by two individuals,namely one person driving the snowmobile 10 and a passenger, such thatthe seat 18 may accommodate both of these individuals (e.g., behind oneanother) or the snowmobile 10 may comprise an additional seat for thepassenger.

The user interface 20 allows the user to interact with the snowmobile 10to control the snowmobile 10. More particularly, the user interface 20comprises an accelerator, a brake control, and a steering device thatare operated by the user to control motion of the snowmobile 10 on theground. In this case, the steering device comprises handlebars, althoughit may comprise a steering wheel or other type of steering element inother cases. The user interface 20 also comprises an instrument panel(e.g., a dashboard) which provides indicators (e.g., a speedometerindicator, a tachometer indicator, etc.) to convey information to theuser.

The track system 14 engages the ground to generate traction of thesnowmobile 10. In this embodiment, the track system 14 comprises atrack-engaging assembly 24 and a track 21 disposed around thetrack-engaging assembly 24. More particularly, in this embodiment, withadditional reference to FIG. 2, the track-engaging assembly 24 comprisesa plurality of wheels, including a plurality of drive wheels 22 ₁, 22 ₂and a plurality of idler wheels, which includes rear idler wheels 26₁-26 ₄, lower roller wheels 28 ₁-28 ₆, and upper roller wheels 30 ₁, 30₂. The track-engaging assembly 24 also comprises a plurality of sliderails 33 ₁, 33 ₂. Various components of the track-engaging assembly 24,including the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ and theslide rails 33 ₁, 33 ₂ are supported by a suspension unit 16. The tracksystem 14 has a longitudinal direction and a first longitudinal end anda second longitudinal end that define a length of the track system 14.The track system 14 has a widthwise direction and a width that isdefined by a width of the track 21. The track system 14 has a heightdirection that is normal to its longitudinal direction and its widthwisedirection.

The track 21 engages the ground to provide traction to the snowmobile10. A length of the track 21 allows the track 21 to be mounted aroundthe track-engaging assembly 24. In view of its closed configurationwithout ends that allows it to be disposed and moved around thetrack-engaging assembly 24, the track 21 can be referred to as an“endless” track. With additional reference to FIGS. 3 to 7A, the endlesstrack 21 comprises an inner side 25 and a ground-engaging outer side 27.The inner side 25 faces the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30₁, 30 ₂ and the slide rails 33 ₁, 33 ₂. The ground-engaging outer side27 engages the ground. A top run 65 of the endless track 21 extendsbetween the longitudinal ends of the track system 14 and over the wheels22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂, and a bottom run 66 of theendless track 21 extends between the longitudinal ends of the tracksystem 14 and under the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁,30 ₂ and the slide rails 33 ₁, 33 ₂. The endless track 21 has alongitudinal axis which defines a longitudinal direction of the track 21(i.e., a direction generally parallel to its longitudinal axis) andtransversal directions of the track (i.e., directions transverse to itslongitudinal axis), including a widthwise direction of the track (i.e.,a lateral direction generally perpendicular to its longitudinal axis).The endless track 21 has a thickness direction normal to itslongitudinal and widthwise directions.

The track 21 is elastomeric, i.e., comprises elastomeric material, to beflexible around the track-engaging assembly 24. The elastomeric materialof the track 21 can include any polymeric material with suitableelasticity. In this embodiment, the elastomeric material of the track 21includes rubber. Various rubber compounds may be used and, in somecases, different rubber compounds may be present in different areas ofthe track 21. In other embodiments, the elastomeric material of thetrack 21 may include another elastomer in addition to or instead ofrubber (e.g., polyurethane elastomer).

More particularly, the track 21 comprises an endless body 35 underlyingits inner side 25 and ground-engaging outer side 27. In view of itsunderlying nature, the body 36 will be referred to as a “carcass”. Thecarcass 35 is elastomeric in that it comprises elastomeric material 38which allows the carcass 35 to elastically change in shape and thus theendless track 21 to flex as it is in motion around the track-engagingassembly 24. The elastomeric material 38 can be any polymeric materialwith suitable elasticity. In this embodiment, the elastomeric material38 includes rubber. Various rubber compounds may be used and, in somecases, different rubber compounds may be present in different areas ofthe carcass 35. In other embodiments, the elastomeric material 38 mayinclude another elastomer in addition to or instead of rubber (e.g.,polyurethane elastomer).

In this embodiment, the carcass 35 comprises a plurality ofreinforcements embedded in its elastomeric material 38. Thesereinforcements can take on various forms.

For example, in this embodiment, the carcass 35 comprises a plurality oftransversal stiffening rods 36 ₁-36 _(N) that extend transversally tothe longitudinal direction of the endless track 21 to providetransversal rigidity to the track 21. More particularly, in thisembodiment, the transversal stiffening rods 36 ₁-36 _(N) extend in thewidthwise direction of the track 21. Each of the transversal stiffeningrods 36 ₁-36 _(N) may have various shapes and be made of any suitablyrigid material (e.g., metal, polymer or composite material).

As another example, in this embodiment, the carcass 35 comprises aplurality of reinforcing cables 37 ₁-37 _(M) that are adjacent to oneanother and extend generally in the longitudinal direction of theendless track 21 to enhance strength in tension of the track 21 alongits longitudinal direction. In this case, each of the reinforcing cables37 ₁-37 _(M) is a cord including a plurality of strands (e.g., textilefibers or metallic wires). In other cases, each of the reinforcingcables 37 ₁-37 _(M) may be another type of cable and may be made of anymaterial suitably flexible longitudinally (e.g., fibers or wires ofmetal, plastic or composite material).

As yet another example, in this embodiment, the carcass 35 comprises alayer of reinforcing fabric 43. The reinforcing fabric 43 comprises thinpliable material made usually by weaving, felting, knitting,interlacing, or otherwise crossing natural or synthetic elongated fabricelements, such as fibers, filaments, strands and/or others, such thatsome elongated fabric elements extend transversally to the longitudinaldirection of the track 21 to have a reinforcing effect in a transversaldirection of the track 21. For instance, the reinforcing fabric 43 maycomprise a ply of reinforcing woven fibers (e.g., nylon fibers or othersynthetic fibers). For example, the reinforcing fabric 43 may protectthe transversal stiffening rods 36 ₁-36 _(N), improve cohesion of thetrack 21, and counter its elongation.

The carcass 35 may be molded into shape in a molding process duringwhich the rubber 38 is cured. For example, in this embodiment, a moldmay be used to consolidate layers of rubber providing the rubber 38 ofthe carcass 35, the reinforcing cables 37 ₁-37 _(M) and the layer ofreinforcing fabric 43.

In this embodiment, the endless track 21 is a one-piece “jointless”track such that the carcass 35 is a one-piece jointless carcass. Inother embodiments, the endless track 21 may be a “jointed” track (i.e.,having at least one joint connecting adjacent parts of the track 21)such that the carcass 35 is a jointed carcass (i.e., which has adjacentparts connected by the at least one joint). For example, in someembodiments, the endless track 21 may comprise a plurality of tracksections interconnected to one another at a plurality of joints, inwhich case each of these track sections includes a respective part ofthe carcass 35. In other embodiments, the endless track 21 may be aone-piece track that can be closed like a belt with connectors at bothof its longitudinal ends to form a joint.

The ground-engaging outer side 27 of the track 21 comprises aground-engaging outer surface 31 of the carcass 35 and a plurality oftraction projections 58 ₁-58 _(T) that project outwardly from theground-engaging outer surface 31 to enhance traction on the ground. Thetraction projections 58 ₁-58 _(T), which can be referred to as “tractionlugs” or “traction profiles”, may have any suitable shape (e.g., curvedshapes, shapes with straight parts and curved parts, etc.).

In this embodiment, each of the traction projection 58 ₁-58 _(T) is anelastomeric traction projection in that it comprises elastomericmaterial 41. The elastomeric material 41 can be any polymeric materialwith suitable elasticity. More particularly, in this embodiment, theelastomeric material 41 includes rubber. Various rubber compounds may beused and, in some cases, different rubber compounds may be present indifferent areas of each of the traction projections 58 ₁-58 _(T). Inother embodiments, the elastomeric material 41 may include anotherelastomer in addition to or instead of rubber (e.g., polyurethaneelastomer).

The traction projections 58 ₁-58 _(T) may be provided on theground-engaging outer side 27 in various ways. For example, in thisembodiment, the traction projections 58 ₁-58 _(T) are provided on theground-engaging outer side 27 by being molded with the carcass 35.

The inner side 25 of the track 21 comprises an inner surface 32 of thecarcass 35 and a plurality of inner projections 34 ₁-34 _(D) thatproject inwardly from the inner surface 32 and are positioned to contactat least some of the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and/or some of the slide rails 33 ₁, 33 ₂ to do at least one of driving(i.e., imparting motion to) the track 21 and guiding the track 21. Sinceeach of them is used to do at least one of driving the track 21 andguiding the track 21, the inner projections 34 ₁-34 _(D) can be referredto as “drive/guide projections” or “drive/guide lugs”. In some cases, adrive/guide lug 34 _(i) may interact with a given one of the drivewheels 22 ₁, 22 ₂ to drive the track 21, in which case the drive/guidelug 34 _(i) is a drive lug. In other cases, a drive/guide lug 34 _(i)may interact with a given one of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₂,30 ₁, 30 ₂ and/or a given one of the slide rails 33 ₁, 33 ₂ to guide thetrack 21 to maintain proper track alignment and prevent de-trackingwithout being used to drive the track 21, in which case the drive/guidelug 34 _(i) is a guide lug. In yet other cases, a drive/guide lug 34_(i) may both (i) interact with a given one of the drive wheels 22 ₁, 22₃ to drive the track 21 and (ii) interact with a given one of the idlerwheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ and/or a given one of the sliderails 33 ₁, 33 ₂ to guide the track 21, in which case the drive/guidelug 34 _(i) is both a drive lug and a guide lug.

In this embodiment, each of the drive/guide lugs 34 ₁-34 _(D) is anelastomeric drive/guide lug in that it comprises elastomeric material42. The elastomeric material 42 can be any polymeric material withsuitable elasticity. More particularly, in this embodiment, theelastomeric material 42 includes rubber. Various rubber compounds may beused and, in some cases, different rubber compounds may be present indifferent areas of each of the drive/guide lugs 34 ₁-34 _(D). In otherembodiments, the elastomeric material 42 may include another elastomerin addition to or instead of rubber (e.g., polyurethane elastomer).

The drive/guide lugs 34 ₁-34 _(D) may be provided on the inner side 25in various ways. For example, in this embodiment, the drive/guide lugs34 ₁-34 _(D) are provided on the inner side 25 by being molded with thecarcass 35.

The carcass 35 has a thickness T_(c) which is relatively small. Thethickness T_(c) of the carcass 35 is measured from the inner surface 32to the ground-engaging outer surface 31 of the carcass 35 betweenlongitudinally-adjacent ones of the traction projections 58 ₁-58 _(T).For example, in some embodiments, the thickness T_(c) of the carcass 35may be no more than 0.25 inches, in some cases no more than 0.24 inches,in some cases no more than 0.23 inches, in some cases no more than 0.22inches, in some cases no more than 0.21 inches, in some cases no morethan 0.20 inches, and in some cases even less (e.g., 0.18 or 0.17inches). The thickness T_(c) of the carcass 35 may have any othersuitable value in other embodiments.

The endless track 21 may be constructed and/or manufactured in variousother ways in other embodiments.

For example, FIG. 7B shows an embodiment in which the track 21 is freeof reinforcing fabric between the inner surface 32 and theground-engaging outer surface 31 of the carcass 35 along at least partof the length of the track 21. That is, there is no layer of reinforcingfabric in the carcass 35 along at least part of the length of the track21. In this embodiment, the track 21 is free of reinforcing fabricbetween the inner surface 32 and the ground-engaging outer surface 31along at least a majority of the length of the track 21. Moreparticularly, in this example of implementation, the track 21 is free ofreinforcing fabric between the inner surface 32 and the ground-engagingouter surface 31 along an entirety of the length of the track 21. Thereis thus no layer of reinforcing fabric in the carcass 35 of the track 21in this example of implementation. Specifically, in this case, the track21 is free of reinforcing fabric, i.e., there is no layer of reinforcingfabric in the track 21.

This lack of reinforcing fabric layer may reduce a weight of the track21. The lack of reinforcing fabric layer may also reduce a powerconsumption to drive the track 21. That is, when operated at a givenspeed, the track 21 may consume less power than if it had a reinforcingfabric layer (e.g., the layer of reinforcing fabric 43) embedded in thecarcass 35 and extending along at least a majority (e.g., an entirety)of the length of the track 21 but was otherwise identical. For instance,in some examples of implementation, the track 21 may consume less powerwhen operated at a speed above 40 miles per hour, in some cases above 60miles per hour, and in some cases above 80 miles per hour.

More particularly, in this embodiment, the carcass 35 comprises thereinforcing cables 37 ₁-37 _(M) and the transversal stiffening rods 36₁-36 _(N) embedded in its rubber 38 but is free of any reinforcingfabric layer (i.e., the layer of reinforcing fabric 43 discussed aboveis omitted). In this case, the reinforcing cables 37 ₁-37 _(M) arelocated between the transversal stiffening rods 36 ₁-36 _(N) and theinner surface 32 of the carcass 35 in the thickness direction of thetrack 21. In other cases, as shown in FIG. 7C, the reinforcing cables 37₁-37 _(M) may be located between the transversal stiffening rods 36 ₁-36_(N) and the outer surface 31 of the carcass 35 in the thicknessdirection of the track 21. In such cases, the reinforcing cables 37 ₁-37_(M) may act to protect the transversal stiffening rods 36 ₁-36 _(N).

The track 21 free of any reinforcing fabric layer may be configured invarious other ways in other embodiments. For example, in someembodiments, the track 21 may also be free of transversal stiffeningrods, as shown in FIG. 7D.

In other embodiments, the track 21 may be free of reinforcing fabricbetween the inner surface 32 and the ground-engaging outer surface 31 ofthe carcass 35 along part of the length of the track 21 but stillinclude some reinforcing fabric (e.g., between the inner surface 32 andthe ground-engaging surface 31 along one or more segments of the lengthof the track 21, or within one or more of the drive/guide lugs 34 ₁-34_(D) and/or one or more of the traction projections 58 ₁-58 _(T)).

Elastomeric material of a given portion of the endless track 21,including the elastomeric material 38 of the carcass 35, the elastomericmaterial 41 of one of the traction projection 58 ₁-58 _(T), and theelastomeric material 42 of one of the drive/guide lugs 34 ₁-34 _(D), hasvarious material properties, including a hardness (e.g., durometers in aShore A hardness scale) and a modulus of elasticity, which can have anysuitable value.

If the elastomeric material of the given portion of the track 21 isconstituted of a single elastomer, the hardness of the elastomericmaterial of the given portion of the track 21 is the hardness of thissingle elastomer. Alternatively, if the elastomeric material of thegiven portion of the track 21 is constituted of two or more differentelastomers, the hardness of the elastomeric material of the givenportion of the track 21 is taken as an average hardness, which isobtained by multiplying a proportion of each elastomer in theelastomeric material of the given portion of the track 21 by thatelastomer's hardness and then summing the results. That is, if theelastomeric material of the given portion of the track 21 is constitutedof N elastomers, the average hardness is

$A_{avg} = {\sum\limits_{i = 1}^{N}\; {P_{i}A_{i}}}$

where A_(i) is the hardness of elastomer “i” and P_(i) is the proportion(%) of elastomer “i” in the elastomeric material of the given portion ofthe track 21. In situations where this calculated value is not aninteger and the hardness scale is only in integers, this calculatedvalue rounded to the nearest integer gives the average hardness. Anelastomer's hardness can be obtained from a standard ASTM D-2240 test(or equivalent test).

Similarly, if the elastomeric material of the given portion of the track21 is constituted of a single elastomer, the modulus of elasticity ofthe elastomeric material of the given portion of the track 21 is themodulus of elasticity of this single elastomer. Alternatively, if theelastomeric material of the given portion of the track 21 is constitutedof two or more different elastomers, the modulus of elasticity of theelastomeric material of the given portion of the track 21 is taken as anaverage modulus of elasticity, which is obtained by multiplying aproportion (%) of each elastomer in the elastomeric material of thegiven portion of the track 21 by that elastomer's modulus of elasticityand then summing the results. That is, if the elastomeric material ofthe given portion of the track 21 is constituted of N elastomers, theaverage modulus of elasticity is

$\lambda_{avg} = {\sum\limits_{i = 1}^{N}\; {P_{i}\lambda_{i}}}$

where λ_(i) is the modulus of elasticity of elastomer “i” and P_(i) isthe proportion (%) of elastomer “i” in the elastomeric material of thegiven portion of the track 21. For instance, in an embodiment in whichthe elastomeric material of the given portion of the track 21 isconstituted of two types of rubbers, say rubber “A” having a modulus ofelasticity of 1.9 MPa and being present in a proportion of 15% andrubber “B” having a modulus of elasticity of 6.3 MPa and being presentin a proportion of 85%, the average modulus of elasticity of theelastomeric material of the given portion of the track 21 is 5.64 MPa.An elastomer's modulus of elasticity can be obtained from a standardASTM D-412-A test (or equivalent test) based on a measurement at 100%elongation of the elastomer.

Each of the drive wheels 22 ₁, 22 ₂ is rotatable on an axle of thesnowmobile 10 for driving the endless track 21. That is, power generatedby the prime mover 15 and delivered over the powertrain 12 of thesnowmobile 10 rotates the axle, which rotates the drive wheels 22 ₁, 22₂, which impart motion of the track 21. In this embodiment, each drivewheel 22 _(i) comprises a drive sprocket engaging some of thedrive/guide lugs 34 ₁-34 _(D) of the inner side 25 of the track 21 inorder to drive the track 21. In other embodiments, the drive wheel 22_(i) may be configured in various other ways. For example, inembodiments where the track 21 comprises drive holes, the drive wheel 22_(i) may have teeth that enter these holes in order to drive the track21. As yet another example, in some embodiments, the drive wheel 22 _(i)may frictionally engage the inner side 25 of the track 21 in order tofrictionally drive the track 21. The drive wheels 22 ₁, 22 ₂ may bearranged in other configurations and/or the track system 14 may comprisemore or less drive wheels (e.g., a single drive wheel, more than twodrive wheels, etc.) in other embodiments.

The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ are not driven bypower supplied by the prime mover 15, but are rather used to do at leastone of guiding the track 21 as it is driven by the drive wheels 22 ₁, 22₂, tensioning the track 21, and supporting part of the weight of thesnowmobile 10 on the ground via the track 21. More particularly, in thisembodiment, the rear idler wheels 26 ₁-26 ₄ are trailing idler wheelsthat maintain the track 21 in tension, guide the track 21 as it wrapsaround them, and can help to support part of the weight of thesnowmobile 10 on the ground via the track 21. The lower roller wheels 28₁-28 ₆ roll on the inner side 25 of the track 21 along the bottom run 66of the track 21 to apply the bottom run 66 on the ground. The upperroller wheels 30 ₁, 30 ₂ roll on the inner side 25 of the track 21 alongthe top run 65 of the track 21 to support and guide the top run 65 asthe track 21 moves. The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂may be arranged in other configurations and/or the track assembly 14 maycomprise more or less idler wheels in other embodiments.

The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ move on respectiveones of a plurality of idler wheel paths 50 ₁-50 ₄ of the inner surface32 of the carcass 35 of the endless track 21. Each of the idler wheelpaths 50 ₁-50 ₄ extends adjacent to respective ones of the drive/guidelugs 34 ₁-34 _(D) to allow these lugs to guide motion of the track 21around the track-engaging assembly 24. As the roller wheels 28 ₁-28 ₆,30 ₁, 30 ₂ roll on respective ones of the idler wheel paths 50 ₁-50 ₄,these paths can be referred to as “rolling paths”.

The slide rails 33 ₁, 33 ₂ slide on the inner side 25 of the endlesstrack 21 along the bottom run 66 of the track 21 to apply the bottom run66 onto the ground. In this embodiment, the slide rails 33 ₁, 33 ₂ arecurved upwardly in a front region of the track system 14 to guide thetrack 21 towards the drive wheels 22 ₁, 22 ₂. In some cases, as shown inFIG. 8, the endless track 21 may comprise slide members 39 ₁-39 _(S)that slide against the slide rails 33 ₁, 33 ₂ to reduce friction. Theslide members 39 ₁-39 _(S), which can sometimes be referred to as“clips”, may be mounted via holes 40 ₁-40 _(H) arranged in two rowsextending longitudinally and spaced apart laterally of the track 21. Inother cases, as shown in FIG. 9, the endless track 21 may be free ofsuch slide members. The slide rails 33 ₁, 33 ₂ may be arranged in otherconfigurations and/or the track assembly 14 may comprise more or lessslide rails in other embodiments.

Various considerations may be important when it comes to use andperformance of the snowmobile 10.

For example, in use, the snowmobile 10 generates noise, including noisegenerated by the track system 14. Various factors may contribute to thenoise generated by the track system 14. For example, in some cases:impacts between the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ andthe transversal stiffening rods 36 ₁-36 _(N) of the endless track 21;impacts between the slide rails 33 ₁, 33 ₂ and the transversalstiffening rods 36 ₁-36 _(N) of the track 21; impacts between the sliderails 33 ₁, 33 ₂ and the clips 39 ₁-39 _(S) of the track 21, if any;impacts between the traction projections 58 ₁-58 _(T) of the track 21and the ground; and contact between the track 21 and the drive wheels 22₁, 22 ₂ may be contributors to the noise generated by the track system14.

As another example, traction and floatation provided by the track system14 depend on rigidity of the endless track 21. While longitudinalflexibility of the track 21 is desirable in order to efficiently drivethe track around the track-engaging assembly 24, transversal rigidity ofthe track 21 is desirable in order to have a proper ground-contactingarea for traction and floatation.

The snowmobile 10, including the track system 14, may therefore beconfigured to have a reduced noise profile so as to generate less noise,enhanced track rigidity characteristics to improve its traction andfloatation, and/or other features improving use and performance of thesnowmobile 10. This may be achieved in various ways in variousembodiments, examples of which will now be discussed.

1. Shape of Transversal Stiffening Rod

In some embodiments, the transversal stiffening rods 36 ₁-36 _(N) of theendless track 21 may be shaped in order to reduce noise generationand/or for other purposes (e.g., weight reduction, controlledtransversal rigidity, etc.). Various shapes of the transversalstiffening rods 36 ₁-36 _(N) can be implemented in various embodiments,examples of which are discussed below.

1.1 Transversal Stiffening Rods Shaped to Increase Thickness ofElastomeric Material

In some embodiments, the transversal stiffening rods 36 ₁-36 _(N) may beshaped so as to increase a thickness of elastomeric material of theendless track 21 at locations of the rods 36 ₁-36 _(N). That is, thetransversal stiffening rods 36 ₁-36 _(N) may be shaped such that athickness of elastomeric material where they are located is greater thanthat which would exist if they were replaced with conventionaltransversal stiffening rods having a generally semicircular orhalf-moon-shaped cross-section, such as those shown in FIG. 6, but thetrack 21 was otherwise identical and had the same transversal rigidity.The greater thickness of elastomeric material can provide enhanced shockabsorption, and therefore reduce noise generation, when the idler wheels26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ and the slide rails 33 ₁, 33 ₂ crossthe transversal stiffening rods 36 ₁-36 _(N). Also, in some cases, thetransversal stiffening rods 36 ₁-36 _(N) may have a smallercross-section than conventional rods and this may make them less rigidand thus less noisy when crossed by the idler wheels 26 ₁-26 ₄, 28 ₁-28₆, 30 ₁, 30 ₂ and the slide rails 33 ₁, 33 ₂.

Various shapes of the transversal stiffening rods 36 ₁-36 _(N) can beimplemented to increase the thickness of elastomeric material in variousembodiments, examples of which are discussed below.

1.1.1 Rod Cross-Section being Elongate (i.e., Having a High AspectRatio)

In some embodiments, as shown in FIGS. 10 and 11, a transversalstiffening rod 36 _(x) may have a cross-section which is elongate, i.e.,has a high aspect ratio C_(L)/C_(S). The cross-section of thetransversal stiffening rod 36 _(x) is taken perpendicularly to alongitudinal axis 86 of the rod 36 _(x) and is elongate since a longestdimension C_(L) of the cross-section is significantly greater than asmallest dimension C_(S) of the cross-section. In this example, thelongest dimension C_(L) of the cross-section of the transversalstiffening rod 36 _(x) is in the longitudinal direction of the endlesstrack 21 and the smallest dimension C_(S) of the cross-section of thetransversal stiffening rod 36 _(x) is in the thickness direction of theendless track 21. The cross-section of the transversal stiffening rod 36_(x) is thus elongated in the longitudinal direction of the track 21.

The aspect ratio C_(L)/C_(S) of the cross-section of the transversalstiffening rod 36 _(x), which is a ratio of the longest dimension C_(L)of the cross-section to the smallest dimension C_(S) of thecross-section, can have any suitable value in various embodiments. Forexample, in some embodiments, the aspect ratio C_(L)/C_(S) may be atleast 4, in some cases at least 5, in some cases at least 6, in somecases at least 7, in some cases at least 8, in some cases at least 10,and in some cases even more (e.g., 12, 15 or more).

In this embodiment, the cross-section of the transversal stiffening rod36 _(x) is substantially flat. That is, the cross-section of the rod 36_(x) has major surfaces generally parallel to one another and distinctlylarger than its minor surfaces.

More particularly, in this embodiment, the cross-section of thetransversal stiffening rod 36 _(x) is oblong. More specifically, in thisembodiment, the cross-section of the transversal stiffening rod 36 _(x)has a generally oblong rectangular shape. A width W_(R) of thecross-section of the transversal stiffening rod 36 _(x) is in thelongitudinal direction of the endless track 21, and corresponds to thelongest dimension C_(L) of the cross-section. A thickness T_(R) of thecross-section of the transversal stiffening rod 36 _(x) is in thethickness direction of the endless track 21, and corresponds to thesmallest dimension C_(S) of the cross-section. In this example, theaspect ratio W_(R)/T_(R) is about 8. In view of the generally oblongrectangular shape and thinness of its cross-section, in this example,the transversal stiffening rod 36 _(x) is plate-like and similar to aruler and can be referred to as a “plate-like” or “ruler” rod.

Also, in this embodiment, the cross-section of the transversalstiffening rod 36 _(x) is constant (i.e., does not substantially change)along at least a majority of a length of the rod 36 _(x). Moreparticularly, in this example, the cross-section of the transversalstiffening rod 36 _(x) is constant along an entirety of the length ofthe rod 36 _(x). In other embodiments, the cross-section of thetransversal stiffening rod 36 _(x) may vary along the longitudinal axis86 of the rod 36 _(x) such that it is different (e.g., larger, smaller,and/or differently shaped) at respective locations along thelongitudinal axis 86 of the rod 36 _(x).

The cross-section of each of the transversal stiffening rods 36 ₁-36_(N) may have various other shapes such that it is elongate, i.e., itsaspect ratio C_(L)/C_(S) is high, in other embodiments. For example, inother embodiments, the cross-section of a transversal stiffening rod 36_(x) may be oblong but not rectangular (e.g., it may be oblong withbent, curved or pointy lateral edges).

1.1.2 Thin Rod

In some embodiments, as shown in FIGS. 12 and 13, a transversalstiffening rod 36 _(x) may be “thin”, i.e., the thickness T_(R) of thecross-section of the transversal stiffening rod 36 _(x) in the thicknessdirection of the endless track 21 may be small. In some cases, this canhappen with the cross-section of the transversal stiffening rod 36 _(x)being elongate, i.e., having a high aspect ratio C_(L)/C_(S), asdiscussed above in section 1.1.1. In other cases, this can happenwithout the cross-section of the transversal stiffening rod 36 _(x)being elongate, i.e., having a high aspect ratio C_(L)/C_(S).

The thickness T_(R) can have any suitable value. For example, in someembodiments, the thickness T_(R) may be less than 3.5 mm, in some casesno more than 3 mm, in some cases no more than 2.5 mm, in some cases nomore than 2 mm, and in some cases even less (e.g., 1.5 mm or less).

The thickness T_(R) of the cross-section of the transversal stiffeningrod 36 _(x) can also be expressed relative to the thickness T_(C) of thecarcass 35. For example, in some embodiments, a ratio T_(R)/T_(C) of thethickness T_(R) of the cross-section of the transversal stiffening rod36 _(x) to the thickness T_(C) of the carcass 35 may be less than 0.7,in some cases no more than 0.6, in some cases no more than 0.5, in somecases no more than 0.4, and in some cases even less (e.g., 0.2 or less).

In this embodiment, the cross-section of the transversal stiffening rod36 _(x) is generally semicircular or half-moon-shaped. The thicknessT_(R) thus generally corresponds to a radius of the cross-section of thetransversal stiffening rod 36 _(x). Hence, in this embodiment, thetransversal stiffening rod 36 _(x) is thin but its cross-section doesnot have a high aspect ratio C_(L)/C_(S) as discussed above in section1.1.1.

The cross-section of each of the transversal stiffening rods 36 ₁-36_(N) may have various other shapes such that its thickness T_(R) issmall in other embodiments.

For example, in other embodiments, the cross-section of a transversalstiffening rod 36 _(x) may be generally circular, square, oblongrectangular, etc.

1.1.3 Rod Defining an Internal Space

In some embodiments, as shown in FIGS. 14 and 15, a transversalstiffening rod 36 _(x) may form a cavity (i.e., an internal space) 44which, in this example, receives elastomeric material 46. In thisembodiment, the cavity 44 is open toward the inner side 25 of theendless track 21 in order to increase a thickness of elastomericmaterial between the transversal stiffening rod 36 _(x) and the innerside 25 of the track 21. The elastomeric material 46, which is a portionof the elastomeric material 38 of the carcass 35, is thus locatedbetween the transversal stiffening rod 36 _(x) and the inner surface 32of the carcass 35.

More particularly, in this embodiment, the transversal stiffening rod 36_(x) forms the cavity 44 by having a cross-section that is curved. Inthis example, the cross-section of the transversal stiffening rod 36_(x) is generally arc-shaped. In addition to the increase in thethickness of elastomeric material, this shape may make the transversalstiffening rod 36 _(x) more rigid (e.g., compared to a plate-like rod asdiscussed above in section 1.1.1).

The cross-section of the transversal stiffening rod 36 _(x) may havevarious other shapes which define the cavity 44 in other embodiments.For instance, in some embodiments, the cross-section of the transversalstiffening rod 36 _(x) may have other curvatures, may have straightsegments, or may have a combination of straight segments and curvedsegments to define the cavity 44.

FIGS. 16 and 17 show another embodiment in which the cavity 44 is closedaround the cross-section of the transversal stiffening rod 36 _(x).Basically, the transversal stiffening rod 36 _(x) is hollow and has theelastomeric material 46 in its hollow interior. In this embodiment, thecross-section of the transversal stiffening rod 36 _(x) has a generallysemicircular outer wall and the cavity 44 is also generallysemicircular. The cross-section of the transversal stiffening rod 36_(x) and the cavity 44 may have various other shapes in otherembodiments.

The transversal stiffening rod 36 _(x) with the cavity 44 may be madeusing various processes. For example, in some embodiments, thetransversal stiffening rod 36 _(x) may be extruded using an extrusionprocess or pultruded using a pultrusion process. The elastomericmaterial 46 may be provided in the cavity 46 by having some of theelastomeric material 38 of the carcass 35 migrate in the cavity 46during molding of the track 21 (e.g., in cases where the cavity 44 isopen as in FIGS. 14 and 15), or by placing a piece of elastomericmaterial in the cavity 44 of before molding of the track 21 (e.g., incases where the cavity 44 is closed as in FIGS. 16 and 17).

As a variant to having elastomeric material 46 in the cavity 44 of atransversal stiffening rod 36 _(x), in some embodiments, the cavity 44may be empty or may contain material (e.g., a fluid) other thanelastomeric material. In some cases, this may involve the cavity 44being closed not only around the cross-section of the transversalstiffening rod 36 _(x) but also at both longitudinal ends of thetransversal stiffening rod 36 _(x).

1.1.4 Rod Including a Recess at Idler Wheel Path

In some embodiments, as shown in FIG. 18, a transversal stiffening rod36 _(x) may comprise a plurality of recesses 51 ₁-51 ₄ aligned withrespective ones of the idler wheel paths 50 ₁-50 ₄. That is, therecesses 51 ₁-51 ₄ are located in the widthwise direction of the endlesstrack 21 where the idler wheel paths 50 ₁-50 ₄ are located, i.e., eachof these recesses overlaps a respective one of the idler wheel paths 50₁-50 ₄ in the widthwise direction of the track 21. Each recess 51 _(i)is defined by an inner surface of the transversal stiffening rod 36 _(x)that recedes towards the ground-engaging outer side 27 of the endlesstrack 21. This results in the thickness of elastomeric material betweenthe transversal stiffening rod 36 _(x) and the idler wheel path 50 _(i)being greater than the thickness of elastomeric material between thetransversal stiffening rod 36 _(x) and a portion of the inner surface 32of the carcass 35 outside of the idler wheel paths 50 ₁-50 ₄.

The recess 51 _(i) has a depth D_(r) that may have any suitable value invarious embodiments. For example, in some embodiments, the depth D_(r)may be at least 0.03 inches, in some cases at least 0.045 inches, insome cases at least 0.06 inches, and in some cases even more (e.g., upto 0.125 inches).

The depth D_(r) of the recess 51 _(i) can also be expressed relative tothe thickness T_(R) of the transversal stiffening rod 36 _(x). Forexample, in some embodiments, a ratio D_(r)/T_(R) of the depth D_(r) ofthe recess 51 _(i) to the thickness T_(R) of the transversal stiffeningrod 36 _(x) may be at least 0.1, in some cases at least 0.15, in somecases at least 0.2, and in some cases even more (e.g., up to 0.8).

In this embodiment, the recess 51 _(i) is defined by a dimensionalreduction of the cross-section of the transversal stiffening rod 36_(x). In cases where the transversal stiffening rod 36 _(x) is molded,the recess 51 ₁ may be molded during molding of the transversalstiffening rod 36 _(x) or may be cut or otherwise formed after moldingof the transversal stiffening rod 36 _(x).

FIG. 19 shows another embodiment in which the recess 51 _(i) is definedby a deflection of the transversal stiffening rod 36 _(x). Moreparticularly, in this embodiment, the transversal stiffening rod 36 _(x)is curved towards the ground-engaging outer side 27 of the track 21 todefine the recess 51 ₁. The transversal stiffening rod 36 _(x) may bedeflected in various other manners in other embodiments to define therecess 51 _(i) (e.g., have a V-shaped bent). In cases where thetransversal stiffening rod 36 _(x) is molded, the deflection of thetransversal stiffening rod 36 _(x) which defines the recess 51 _(i) maybe created during molding of the transversal stiffening rod 36 _(x).

1.1.5 Thickness of Elastomeric Material Between Rod Inner Surface andCarcass Inner Surface Varying Longitudinally

In some embodiments, as shown in FIGS. 20A and 21, a transversalstiffening rod 36 _(x) may be shaped such that a thickness ofelastomeric material T_(IR) between an inner surface 52 of thetransversal stiffening rod 36 _(x) (i.e., a surface of the transversalstiffening rod 36 _(x) facing the inner side 25 of the track 21) and theinner surface 32 of the carcass 35 varies in the longitudinal directionof the track 21.

In this case, the thickness of elastomeric material T_(IR) decreases inthe longitudinal direction of the track 21 along a direction of motionof the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂ when the snowmobile 10travels forward. This may help to reduce an intensity of a shock when agiven one of the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂ arrives at thetransversal stiffening rod 36 _(x). Basically, a transition of theroller wheel between a relatively soft region of the track 21 before thetransversal stiffening rod 36 _(x) and a relatively hard region of thetrack at the transversal stiffening rod 36 _(x) is made progressively.

A variation ΔT_(IR) of the thickness of elastomeric material T_(IR)across a dimension L_(R) of the cross-section of the transversalstiffening rod 36 _(x) in the longitudinal direction of the track 21 mayhave any suitable value in various embodiments. The variation ΔT_(IR)can be calculated ΔT_(IR)=(T_(IR-max)−T_(IR-min))/T_(IR-min)×100%, whereT_(IR-max) and T_(IR-min) are respectively the maximum and minimumvalues of the thickness of elastomeric material T_(IR) across thedimension L_(R) of the cross-section of the transversal stiffening rod36 _(x). For example, in some embodiments, the variation ΔT_(IR) may beat least 10%, in some cases at least 30%, in some cases at least 50%,and in some cases even more (e.g., up to 100%).

In this embodiment, the cross-section of the transversal stiffening rod36 _(x) has a wedge-like shape such that the thickness of elastomericmaterial T_(IR) progressively decreases across its dimension L_(R).

FIG. 20B shows another embodiment in which the inner surface 52 of atransversal stiffening rod 36 _(x) is uneven such that the thickness ofelastomeric material T_(IR) between the inner surface 52 of thetransversal stiffening rod 36 _(x) and the inner surface 32 of thecarcass 35 varies in the longitudinal direction of the track 21. In thisembodiment, the inner surface 52 of the transversal stiffening rod 36_(x) is curved. More particularly, in this example, the cross-section ofthe transversal stiffening rod 36 _(x) is generally semicircular orhalf-moon-shaped with the inner surface 52 being arched.

The cross-section of the transversal stiffening rod 36 _(x) may havevarious other shapes to create the variation ΔT_(IR) of the thickness ofelastomeric material T_(IR) in other embodiments.

1.2 Short Rods

In some embodiments, as shown in FIG. 36, a transversal stiffening rod36 _(x) may be a “short” rod that does not extend across all the widthof the endless track 21 such that it does not extend beneathlaterally-outmost track-contacting devices of the track-engagingassembly 24, i.e., laterally-outmost ones of the idler wheels 26 ₁-26 ₄,28 ₁-28 ₆, 30 ₁, 30 ₂ (i.e., those idler wheels which are closest tolateral edges of the track 21) and/or the slide rails 33 ₁, 33 ₂. Thismay avoid impacts that would otherwise occur between the transversalstiffening rod 36 _(x) and these wheels and/or slide rails and maytherefore reduce noise generation.

A ratio of the length of the transversal stiffening rod 36 _(x) to thewidth of the track 21 may have any suitable value. For example, in someembodiments, the ratio of the length of the transversal stiffening rod36 _(x) to the width of the track 21 may be no more than 90%, in somecases no more than 85%, in some cases no more than 80%, and in somecases even less (e.g., no more than 50%).

In this embodiment, the transversal stiffening rod 36 _(x) extendsbeneath the slide rails 33 ₁, 33 ₂ but does not extend beneath the idlerwheels 26 ₁, 26 ₄, 28 ₁, 28 ₂, 28 ₄, 28 ₅ which are laterally outmost(only the idler wheels 28 ₁, 28 ₄ are shown here). In other embodiments,the transversal stiffening rod 36 _(x) may be shorter. For instance,FIG. 37 shows an embodiment in which the transversal stiffening rod 36_(x) does not extend beneath the slide rails 33 ₁, 33 ₂ or the idlerwheels 26 ₁, 26 ₄, 28 ₁, 28 ₂, 28 ₄, 28 ₅ which are laterally outmost.

2. Distribution of Transversal Stiffening Rods

In some embodiments, a distribution of the transversal stiffening rods36 ₁-36 _(N) within the endless track 21 may help to reduce noisegeneration and/or provide other benefits (e.g., controlled transversalrigidity, etc.). Various distributions of the transversal stiffeningrods 36 ₁-36 _(N) can be implemented in various embodiments, examples ofwhich are discussed below.

2.1 Rods Stacked in Thickness Direction of Track

In some embodiments, as shown in FIG. 22A, two or more of thetransversal stiffening rods 36 ₁-36 _(N) may be stacked in the thicknessdirection of the endless track 21 with deformable material 53 inbetween. That is, two or more of the transversal stiffening rods 36 ₁-36_(N) may be spaced apart in the track's thickness direction withdeformable material 53 in between them. This provides enhancedtransversal rigidity but also, by virtue of the deformable material 53,shock absorption, which may help to reduce noise generation.

In this embodiment, a first transversal stiffening rod 36 _(i) and asecond transversal stiffening rod 36 _(j) are spaced apart in thethickness direction of the track 21 and the deformable material 53between them comprises elastomeric material. In this example ofimplementation, the elastomeric material 53 is rubber. The elastomericmaterial 53 may be another elastomer in other examples ofimplementation.

In some cases, the rubber 53 between the transversal stiffening rods 36_(i), 36 _(j) may have the same elasticity and/or the same hardness asother elastomeric material of the endless track 21 (e.g., a portion ofthe elastomeric material 38 of the carcass 35 above the transversalstiffening rod 36 _(j) or a portion of the elastomeric material 41 ofthe traction projection 58 _(i) below the transversal stiffening rod 36_(i)).

In other cases, the rubber 53 between the transversal stiffening rods 36_(i), 36 _(j) may be more elastic, i.e., have a lower modulus ofelasticity, and/or less hard, i.e., a lower hardness, than otherelastomeric material of the endless track 21 (e.g., a portion of theelastomeric material 38 of the carcass 35 above the transversalstiffening rod 36 _(j) or a portion of the elastomeric material 41 ofthe traction projection 58 _(i) below the transversal stiffening rod 36_(i)). This may help in terms of shock absorption. For example, in someembodiments, a ratio of the modulus of elasticity of the rubber 53between the transversal stiffening rods 36 _(i), 36 _(j) and the modulusof elasticity of a portion of the elastomeric material 38 of the carcass35 above the transversal stiffening rod 36 _(j) or a portion of theelastomeric material 41 of the traction projection 58 _(i) below thetransversal stiffening rod 36 _(i) may be no more than 0.9, in somecases no more than 0.8, in some cases no more than 0.7, and in somecases even less (e.g., no more than 0.5); and/or a ratio of the hardnessof the rubber 53 between the transversal stiffening rods 36 _(i), 36_(j) and the hardness of a portion of the elastomeric material 38 of thecarcass 35 above the transversal stiffening rod 36 _(j) or a portion ofthe elastomeric material 41 of the traction projection 58 _(i) below thetransversal stiffening rod 36 _(i) may be no more than 0.9, in somecases no more than 0.8, in some cases no more than 0.7, and in somecases even less (e.g., no more than 0.5).

In other cases, the rubber 53 between the transversal stiffening rods 36_(i), 36 _(j) may be more rigid, i.e., have a higher modulus ofelasticity, and/or harder, i.e., a higher hardness, than otherelastomeric material of the endless track 21 (e.g., a portion of theelastomeric material 38 of the carcass 35 above the transversalstiffening rod 36 _(j) or a portion of the elastomeric material 41 ofthe traction projection 58 _(i) below the transversal stiffening rod 36_(i)). This may help in terms of transverse rigidity. For example, insome embodiments, a ratio of the modulus of elasticity of the rubber 53between the transversal stiffening rods 36 _(i), 36 _(j) and the modulusof elasticity of a portion of the elastomeric material 38 of the carcass35 above the transversal stiffening rod 36 _(j) or a portion of theelastomeric material 41 of the traction projection 58 _(i) below thetransversal stiffening rod 36 _(i) may be at least 1.1, in some cases atleast 1.2, in some cases at least 1.3, and in some cases even more(e.g., at least 1.5); and/or a ratio of the hardness of the rubber 53between the transversal stiffening rods 36 _(i), 36 _(j) and thehardness of a portion of the elastomeric material 38 of the carcass 35above the transversal stiffening rod 36 _(j) or a portion of theelastomeric material 41 of the traction projection 58 _(i) below thetransversal stiffening rod 36 _(i) may be at least 1.1, in some cases atleast 1.2, in some cases at least 1.3, and in some cases even more(e.g., at least 1.5).

A spacing S_(RT) of the transversal stiffening rods 36 _(i), 36 _(j) inthe thickness direction of the track 21 may have any suitable value. Inthis case, the spacing S_(RT) corresponds to a thickness of the rubber53. For example, in some embodiments, the spacing S_(RT) may be at least0.030 inches, in some cases at least 0.060 inches, in some cases atleast 0.125 inches, and in some cases even more.

The spacing S_(RT) of the transversal stiffening rods 36 _(i), 36 _(j)in the thickness direction of the track 21 can also be expressedrelative to the thickness T_(C) of the carcass 35. For example, in someembodiments, a ratio S_(RT)/T_(C) of the spacing S_(RT) of thetransversal stiffening rods 36 _(i), 36 _(j) to the thickness T_(C) ofthe carcass 35 may be at least 0.15, in some cases at least 0.30, insome cases at least 0.60, and in some cases even more.

The deformable material 53 can be positioned between the transversalstiffening rods 36 _(i), 36 _(j) during manufacturing of the endlesstrack 21 in various ways. For example, in embodiments in which theendless track 21 is molded in a mold by placing different layers ofmaterial in the mold, the deformable material 53 may be positioned overthe transversal stiffening rod 36 _(i) in the mold before placing thetransversal stiffening rod 36 _(j) in the mold, or vice versa.

In this embodiment, each of the transversal stiffening rods 36 _(i), 36_(j) has a cross-section with a high aspect ratio and a generallyrectangular shape, i.e., it is a plate-like or “ruler” rod, as discussedabove in section 1.1.1. The transversal stiffening rods 36 _(i), 36 _(j)may have any other suitable shapes in other embodiments. Also, in someembodiments, the transversal stiffening rods 36 _(i), 36 _(j) may have acommon shape, while in other embodiments, they may have differentshapes.

Although in this embodiment the deformable material 53 between thetransversal stiffening rods 36 _(i), 36 _(j) comprises elastomericmaterial, in other embodiments, the deformable material 53 may compriseany other deformable substance. For example, in some embodiments, thedeformable material 53 may comprise a gel, a fluid (e.g., a pouch orother container containing a liquid or gas), or another substance thatcan deform under load.

Also, in some embodiments, one or more of the reinforcing cables 37 ₁-37_(M) and/or a layer of reinforcing fabric 43 of the track 21 may extendbetween the transversal stiffening rods 36 _(i), 36 _(j) stacked overone another. For example, FIG. 22B shows an embodiment in which areinforcing cable 37 _(i) extends between the transversal stiffeningrods 36 _(i), 36 _(j), while FIG. 22C shows an embodiment in which alayer of reinforcing fabric 43 extends between the transversalstiffening rods 36 _(i), 36 _(j).

While in this embodiment there are two transversal stiffening rods 36_(i), 36 _(j) stacked over one another, in other embodiments, there maybe three or more of the transversal stiffening rods 36 ₁-36 _(N) thatare stacked in the thickness direction of the track 21 with deformablematerial 53 between adjacent ones of these three or more transversalstiffening rods.

2.2 Rods Located Between Longitudinally-Adjacent Traction Projections

In some embodiments, as shown in FIG. 23A, in addition to given ones ofthe transversal stiffening rods 36 ₁-36 _(N) being aligned withrespective ones of the traction projections 58 ₁-58 _(T) in thelongitudinal direction of the track 21 (i.e., being located, in thelongitudinal direction of the track 21, where respective ones of thetraction projections 58 ₁-58 _(T) are located such that a stiffening rodoverlaps a traction projection in the longitudinal direction of thetrack 21), other ones of the transversal stiffening rods 36 ₁-36 _(N)may be located, in the longitudinal direction of the track 21, betweenadjacent ones of the traction projections 58 ₁-58 _(T). This may provideenhanced transversal rigidity while not being detrimental in terms ofnoise generation. For example, in some cases, the idler wheels 28 ₁-28₆, 30 ₁, 30 ₂ spending more time on relatively rigid parts of the track21 as they move along respective ones of the rolling paths 50 ₁-50 ₄ ofthe inner surface 32 of the carcass 35 may help to reduce noisegeneration. In other cases, the transversal stiffening rods 36 ₁-36 _(N)may be shaped such that noise generated is not greater than if therewere rods only where the traction projections 58 ₁-58 _(T) are located.

More particularly, in this embodiment, a transversal stiffening rod 36_(x) is located longitudinally between a first traction projection 58_(i) and a second traction projection 58 _(j) that are adjacent to oneanother in the longitudinal direction of the track 21. The transversalstiffening rod 36 _(x) is also located longitudinally between a firsttransversal stiffening rod 36 _(i) and a second transversal stiffeningrod 36 _(j) which are respectively located, in the longitudinaldirection of the track 21, where the traction projections 58 _(i), 58_(j) are located. A distance P_(T) between the traction projections 58_(i), 58 _(j) along the longitudinal direction of the track 21 isreferred to as a “pitch”. In view of its longitudinal position, thetransversal stiffening rod 36 _(x) may be referred to as an“inter-traction-projection” rod or an “interpitch” rod.

In this example, the transversal stiffening rod 36 _(x) is locatedmidway between the traction projections 58 _(i), 58 _(j). In otherexamples, the transversal stiffening rod 36 _(x) may be located closerto a given one of the traction projections 58 _(i), 58 _(j) than theother.

In this embodiment, each of the transversal stiffening rods 36 _(x), 36_(i), 36 _(j) has a cross-section with a high aspect ratio and agenerally rectangular shape, i.e., it is a plate-like or “ruler” rod, asdiscussed above in section 1.1.1. The longitudinal extent of each of thetransversal stiffening rods 36 _(x), 36 _(i), 36 _(j) results in theroller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂ spending even more time onrelatively rigid parts of the track 21 as they move along respectiveones of the rolling paths 50 ₁-50 ₄ of the inner surface 32 of thecarcass 35. Also, the thinness of the transversal stiffening rod 36 _(x)allows it to be entirely embedded in the carcass 35 between the tractionprojections 58 _(i), 58 _(j).

Each of the transversal stiffening rods 36 _(x), 36 _(i), 36 _(j) mayhave any other suitable shape in other embodiments. Also, different onesof the transversal stiffening rods 36 _(x), 36 _(i), 36 _(j) may havedifferent shapes in other embodiments. For example, in some embodiments,the transversal stiffening rods 36 _(i), 36 _(j) may have a common shapewhile the transversal stiffening rod 36 _(x) may have a different shape.For instance, FIG. 23B shows an embodiment in which the transversalstiffening rods 36 _(i), 36 _(j) are thicker and thus more rigid thanthe transversal stiffening rod 36 _(x) since there is more rubber wherethey are located.

Although in this embodiment there is a single inter-traction-projectionrod 36 _(x) between the adjacent traction projections 58 _(i), 58 _(j),in other embodiments, there may be two or more inter-traction-projectionrods between the traction projections 58 _(i), 58 _(j). For instance,FIG. 24 shows an embodiment in which there are twointer-traction-projection rods 36 _(x1), 36 _(x2) between the tractionprojections 58 _(i), 58 _(j).

2.3 Longitudinally-Adjacent Rods have at Least One DifferentCharacteristic

In some embodiments, as shown in FIG. 25, longitudinally-adjacent onesof the transversal stiffening rods 36 ₁-36 _(N) may be different fromone another, i.e., may have at least one characteristic, such as shapeor material, that is different. This may help to reduce noise generationby creating a sound spectrum which is different from that which wouldresult if all the transversal stiffening rods 36 ₁-36 _(N) wereidentical.

In this embodiment, a first transversal stiffening rod 36 _(i) and asecond transversal stiffening rod 36 _(j) which are adjacent to oneanother in the longitudinal direction of the endless track 21 havedifferent shapes. In this example, the transversal stiffening rod 36_(i) has a generally rectangular cross-section (as discussed above insection 1.1.1), while the transversal stiffening rod 36 _(j) has agenerally semicircular cross-section. The transversal stiffening rods 36_(i), 36 _(j) may have any other suitable shapes that are different fromone another in other examples (e.g., the transversal stiffening rods 36_(i), 36 _(j) and the transversal stiffening rod 36 _(x) discussed inconnection with FIG. 23B).

Also, in this embodiment, the transversal stiffening rods 36 _(i), 36_(j) comprise different materials. For example, in this case, thetransversal stiffening rod 36 _(i) may be made of material which is morerigid than material from which is made the transversal stiffening rod 36_(j), given its smaller cross-sectional size.

While in this embodiment the transversal stiffening rods 36 _(i), 36_(j) differ both in shape and material, in other embodiments, thetransversal stiffening rods 36 _(i), 36 _(j) may differ only in shape oronly in material.

Also, although in this embodiment, only two adjacent transversalstiffening rods 36 _(i), 36 _(j) have been considered, in someembodiments, three or more of the stiffening rods 36 ₁-36 _(N) whichsucceed one another in the longitudinal direction of the track 21 may bedifferent from one another (e.g., have three or more different shapesand/or comprise three of more different materials).

3. Material of Transversal Stiffening Rod

In some embodiments, a transversal stiffening rod 36 _(x) may be made ofmaterial which may help to reduce noise generation and/or provide otherbenefits (e.g., controlled transversal rigidity, etc.). For example, insome embodiments, the material of the transversal stiffening rod 36 _(x)may be selected so as to provide transversal rigidity yet reduce thedifference in thickness-wise hardness or rigidity between a region ofthe endless track 21 where the transversal stiffening rod 36 _(x) islocated and adjacent regions of the endless track 21 where there are notransversal stiffening rods. This may help to reduce an intensity of ashock when a given one of the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂arrives at the transversal stiffening rod 36 _(x).

3.1 Reinforced Elastomeric Rod

In some embodiments, as shown in FIG. 26, a transversal stiffening rod36 _(x) may be an elastomeric fiber-reinforced rod which comprises anelongated elastomeric body 55 in which are embedded fibers 56 ₁-56 _(F).The fibers 56 ₁-56 _(F) generally extend transversally to thelongitudinal direction of the track 21 to provide transversal rigidityto the transversal stiffening rod 36 _(x).

The elongated elastomeric body 55 is elastomeric in that it compriseselastomeric material 57. The elastomeric material 57 can be anypolymeric material with suitable elasticity. More particularly, in thisembodiment, the elastomeric material 57 includes rubber. Various rubbercompounds may be used and, in some cases, different rubber compounds maybe present in different areas of each of the elongated elastomeric body55. In other embodiments, the elastomeric material 57 may includeanother elastomer in addition to or instead of rubber (e.g.,polyurethane elastomer).

In some cases, the rubber 57 of the transversal stiffening rod 36 _(x)may be more rigid and/or harder than the elastomeric material 38 or 41of the track 21 in contiguous regions of the track 21 where there is notransversal stiffening rod. For example, in some embodiments, the rubber57 of the transversal stiffening rod 36 _(x) may be less elastic, i.e.,have a higher modulus of elasticity, and/or harder, i.e., have a higherhardness, than the elastomeric material 38 or 41 of the track 21 incontiguous regions of the track 21 where is there is no transversalstiffening rod.

In other cases, the rubber 57 of the transversal stiffening rod 36 _(x)may be less rigid and/or less hard than the elastomeric material 38 or41 of the track 21 in contiguous regions of the track 21 where there isno transversal stiffening rod. For example, in some embodiments, therubber 57 of the transversal stiffening rod 36 _(x) may be more elastic,i.e., have a lower modulus of elasticity, and/or less hard, i.e., have alower hardness, than the elastomeric material 38 or 41 of the track 21in contiguous regions of the track 21 where is there is no transversalstiffening rod.

For example, in some embodiments, a ratio of the modulus of elasticityof the rubber 57 of the transversal stiffening rod 36 _(x) to themodulus of elasticity of the elastomeric material 38 or 41 of the track21 in contiguous regions of the track 21 where is there is notransversal stiffening rod may be at least 0.75, in some cases at least1, and in some cases at least 1.1, and in some cases even more.Alternatively or additionally, in some embodiments, a ratio of thehardness of the rubber 57 of the transversal stiffening rod 36 _(x) tothe hardness of the elastomeric material 38 or 41 of the track 21 incontiguous regions of the track 21 where is there is no transversalstiffening rod may be at least 0.75, in some cases at least 1, in somecases at least 1.1, and in some cases even more.

For instance, in some embodiments, the hardness of the rubber 57 of thetransversal stiffening rod 36 _(x) may at least 60 durometers A, in somecases at least 80 durometers A, in some cases at least 90 durometers A,and in some cases even more. The hardness of the rubber 57 of thetransversal stiffening rod 36 _(x) may have any other suitable value inother embodiments.

The fibers 56 ₁-56 _(F) may be implemented in various manners. In thisembodiment, each of the fibers 56 ₁-56 _(F) extends along at least amajority of a length of the transversal stiffening rod 36 _(x). Moreparticularly, in this case, each of the fibers 56 ₁-56 _(F) extendsalong all of the length of the transversal stiffening rod 36 _(x). Inother embodiments, each of the fibers 56 ₁-56 _(F) may be shorter. Forexample, in other embodiments, the fibers 56 ₁-56 _(F) may be “chopped”or otherwise cut fibers which are few millimeters or centimeters longand are distributed throughout the transversal stiffening rod 36 _(x).

In this embodiment, the fibers 56 ₁-56 _(F) are polymeric fibers. Morespecifically, in this example, the fibers 56 ₁-56 _(F) are aramidfibers. Various other types of polymeric fibers may be used in otherexamples (e.g., polyvinyl alcohol (PVA) fibers). Also, in otherembodiments, the fibers 56 ₁-56 _(F) may be any other suitable type offibers (e.g., metallic fibers, carbon fibers, glass fibers, etc.).

The transversal stiffening rod 36 _(x) may be manufactured using varioustechniques. For example, in some embodiments, the transversal stiffeningrod 36 _(x) may be manufactured using an extrusion process or apultrusion process in which the fibers 56 ₁-56 _(F) are incorporatedduring extrusion or pultrusion of the elongated elastomeric body 55 ofthe rod. In other embodiments, the elongated elastomeric body 55 of therod may be molded with the fibers 56 ₁-56 _(F) inside a mold. Forinstance, two or more strips or other suitably-sized pieces of rubberreinforced with the fibers 56 ₁-56 _(F) having a width generallycorresponding to that of the transversal stiffening rod 36 _(x) may becut from calendared fiber-reinforced rubber and layered on top of oneanother such that, during molding, they form the transversal stiffeningrod 36 _(x).

3.2 Rod Made of Composite Material

In some embodiments, a transversal stiffening rod 36 _(x) may be made ofcomposite material. For instance, in some embodiments, a transversalstiffening rod 36 _(x) may be made of a carbon fiber reinforced plasticmaterial.

4. Zones with Different Elastomeric Material Properties

In some embodiments, elastomeric material of certain zones of theendless track 21 may have different hardness and/or different elasticityin order to reduce noise generation and/or provide other benefits (e.g.,controlled rigidity). Various zones with different hardness and/orelasticity can be implemented in various embodiments, examples of whichare discussed below.

4.1 Hardness and/or Modulus of Elasticity of Elastomeric Material ofGround-Engaging Outer Side is Lower than Hardness and/or Modulus ofElasticity of Elastomeric Material of Carcass

In some embodiments, as shown in FIG. 27, the hardness and/or themodulus of elasticity of elastomeric material of the ground-engagingouter side 27 of the endless track 21 may be lower than the hardnessand/or the modulus of elasticity of the elastomeric material 38 of thecarcass 35 of the track 21. This may help to reduce noise generated.

More particularly, in this embodiment, the hardness and/or the modulusof elasticity of the rubber 41 of a traction projection 58 _(x) is lowerthan the hardness and/or the modulus of elasticity of the rubber 38 ofthe carcass 35. For example, in some embodiments, a ratio of thehardness of the rubber 41 of the traction projection 58 _(x) to thehardness of the rubber 38 of the carcass 35 may be no more than 0.9, insome cases no more than 0.8, and in some cases no more than 0.7. Thehardness of the rubber 41 of the traction projection 58 _(x) may haveany other suitable value in other embodiments.

In embodiments where the rubber 38 of the carcass 35 is constituted of asingle rubber compound, the hardness of the rubber 38 is that of thesingle rubber compound. In embodiments where the rubber 38 of thecarcass 35 is constituted of two or more rubber compounds, the hardnessof the rubber 38 is the average hardness determined based on thehardness of each of these constituent rubber compounds and theirproportions (as discussed previously).

In some cases, in embodiments where the rubber 38 of the carcass 35 isconstituted of two or more rubber compounds, the hardness of the rubber41 of the traction projection 58 _(x) may be lower than the hardness ofan outer layer of the rubber 38 of the carcass 35 which forms theground-engaging outer surface 31 of the carcass 35.

As another example, in some embodiments, a ratio of the modulus ofelasticity of the rubber 41 of the traction projection 58 _(x) to themodulus of elasticity of the rubber 38 of the carcass 35 may be no morethan 0.9, in some cases no more than 0.8, and in some cases no more than0.7. The modulus of elasticity of the rubber 41 of the tractionprojection 58 _(x) may have any other suitable value in otherembodiments.

In embodiments where the rubber 38 of the carcass 35 is constituted of asingle rubber compound, the modulus of elasticity of the rubber 38 isthat of the single rubber compound. In embodiments where the rubber 38of the carcass 35 is constituted of two or more rubber compounds, themodulus of elasticity of the rubber 38 is the average modulus ofelasticity determined based on the modulus of elasticity of each ofthese constituent rubber compounds and their proportions (as discussedpreviously).

In some cases, in embodiments where the rubber 38 of the carcass 35 isconstituted of two or more rubber compounds, the modulus of elasticityof the rubber 41 of the traction projection 58 _(x) may be lower thanthe modulus of elasticity of the outer layer of the rubber 38 of thecarcass 35 which forms the ground-engaging outer surface 31 of thecarcass 35.

4.2 Hardness and/or Modulus of Elasticity of Elastomeric Material atWidthwise Position of Idler Wheel Path is Lower than Hardness and/orModulus of Elasticity of Elastomeric Material at Widthwise PositionOutside of Idler Wheel Path

In some embodiments, as shown in FIG. 28, elastomeric material 59 of theendless track 21 at a widthwise position of an idler wheel path 50 _(i)may be less hard and/or more elastic than elastomeric material 60 of theendless track 21 at a widthwise position outside every idler wheel path.This forms a “shock absorption zone” that provides shock absorption, andthus reduces noise generation, when a given one of the idler wheels 26₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ which runs on the idler wheel path 50 _(i)crosses the transversal stiffening rods 36 ₁-36 _(N). This is an exampleof an embodiment in which a shock absorbency (i.e., a capacity to absorbshocks) of the track 21 at the widthwise position of the idler wheelpath 50 _(i) is greater than a shock absorbency of the track 21 at awidthwise position outside the idler wheel path 50 _(i).

More particularly, in this embodiment, the elastomeric material 59 andthe elastomeric material 60 are adjacent portions of the rubber 38 ofthe carcass 35. In this example, the rubber 59 extends outwardly in thethickness direction of the track 21 from the inner surface 32 of thecarcass 35. The elastomeric material 59 may have any suitable thickness.For instance, in some cases, the thickness of the rubber 59 maycorrespond to at least 10% of the thickness T_(C) of the carcass 35, insome cases at least 20% of the thickness T_(C) of the carcass 35, insome cases at least 30% of the thickness T_(C) of the carcass 35, insome cases at least 40% of the thickness T_(C) of the carcass, and insome cases even more. In some cases, the rubber 59 may extend from theinner surface 32 to the ground-engaging outer surface 31 of the carcass35, i.e., the thickness of the rubber 59 may correspond to the thicknessT_(C) of the carcass 35.

As an example, in some embodiments, a ratio of the hardness of therubber 59 at the widthwise position of the idler wheel path 50 _(i) tothe hardness of the rubber 60 at a widthwise position outside of everyidler wheel path may be no more than 0.9, in some cases no more than0.8, in some cases no more than 0.7, and in some cases even less (e.g.,no more than 0.5).

For instance, in some embodiments, the hardness of the rubber 59 at thewidthwise position of the rolling path 50 _(i) may no more than 80durometers A, in some cases no more than 70 durometers A, in some casesno more than 60 durometers A, and in some cases even less. The hardnessof the rubber 59 may have any other suitable value in other embodiments.

In embodiments where the rubber 59 or 60 of the carcass 35 isconstituted of a single rubber compound, the hardness of the rubber 59or 60 is that of the single rubber compound. In embodiments where therubber 59 or 60 of the carcass 35 is constituted of two or more rubbercompounds, the hardness of the rubber 59 or 60 is the average hardnessdetermined based on the hardness of each of these rubber compounds andtheir proportions (as discussed previously).

As another example, in some embodiments, a ratio of the modulus ofelasticity of the rubber 59 at the widthwise position of the rollingpath 50 _(i) to the modulus of elasticity of the rubber 60 outside ofevery rolling path may be no more than 0.9, in some cases no more than0.8, in some cases no more than 0.7, and in some cases even less (e.g.,no more than 0.5).

In embodiments where the rubber 59 or 60 of the carcass 35 isconstituted of a single rubber compound, the modulus of elasticity ofthe rubber 59 or 60 is that of the single rubber compound. Inembodiments where the rubber 59 or 60 of the carcass 35 is constitutedof two or more rubber compounds, the modulus of elasticity of the rubber59 or 60 is the average modulus of elasticity determined based on themodulus of elasticity of each of these rubber compounds and theirproportions (as discussed previously).

While in embodiments considered above the rubber 59 forming anabsorption zone extends outwardly from the inner surface 32 of thecarcass 35, in other embodiments, the rubber 59 may extend inwardly fromthe ground-engaging outer surface 31 of the carcass 32 without reachingthe inner surface 32 of the carcass 35, as shown in FIG. 29, or may beembedded in the carcass 35 without reaching either of its inner surface32 and ground-engaging outer surface 31, as shown in FIG. 30.

FIG. 31 shows another embodiment in which elastomeric material 61 of theendless track 21 at a widthwise position of an idler wheel path 50 _(i)is less hard and/or more elastic than elastomeric material 62 of theendless track 21 at a widthwise position outside every idler wheel path.In this embodiment, the elastomeric material 61 and the elastomericmaterial 62 are adjacent portions of the rubber 41 of a tractionprojection 58 _(x). In some embodiments, the hardness and/or the modulusof elasticity of each of the rubber 61 and the rubber 62 may be selectedas discussed above in respect of the rubber 59 or 60 of the carcass 35.

In embodiments considered above, the rubber 59 and the rubber 60 of thecarcass 35, and the rubber 61 and the rubber 62 of the tractionprojection 58 _(x), may be provided during manufacturing of the endlesstrack 21 by placing pieces of rubber (e.g., cut sheets or blocks ofrubber) corresponding to these rubber portions in a mold such that,after molding, they form these rubber portions of track 21.

5. Transversal Stiffening Cables

In some embodiments, as shown in FIG. 32A, the endless track 21 maycomprise a layer of transversal stiffening cables 63 ₁-63 _(T) which aregenerally parallel to one another and extend transversally to thelongitudinal direction of the track 21 to provide transverse rigidity.More particularly, in this embodiment, the transversal stiffening cables63 ₁-63 _(T) extend in the widthwise direction of the track 21.

The transversal stiffening cables 63 ₁-63 _(T) may be any suitable typeof cable. For example, in some embodiments, each of the transversalstiffening cables 63 ₁-63 _(T) may be a cord including a plurality ofstrands (e.g., textile fibers or metallic wires). In other embodiments,each of the transversal stiffening cables 63 ₁-63 _(T) may include asingle strand and/or may be made of any other suitable material (e.g.,metal, plastic or composite material).

The layer of transversal stiffening cables 63 ₁-63 _(T) can beimplemented in various ways. For example, in this embodiment, the layerof transversal stiffening cables 63 ₁-63 _(T) is a layer of tire cordfabric in which the transversal stiffening cords 63 ₁-63 _(T) areinterlaced with longitudinal strands 68 ₁-68 _(S) that run generallyalong the longitudinal direction of the track 21. In other embodiments,the transversal stiffening cables 63 ₁-63 _(T) may not be interlacedwith any other fabric members but may rather be unconnected other thanby the rubber of the track 21.

In some embodiments, as shown in FIG. 32B, the track 21 may be free oftransversal stiffening rods but have sufficient transversal rigiditybecause of the transversal stiffening cables 63 ₁-63 _(T).

In other embodiments, as shown in FIG. 32C, the track 21 may include thetransversal stiffening rods 36 ₁-36 _(N) along with the transversalstiffening cables 63 ₁-63 _(T). In some examples of implementation, thetransversal stiffening rods 36 ₁-36 _(N) may be smaller thanconventional rods since the transversal stiffening cables 63 ₁-63 _(T)assist in providing transversal rigidity. For instance, in this case,each of the transversal stiffening rods 36 ₁-36 _(N) has a cross-sectionwith a high aspect ratio and a generally rectangular shape, i.e., it isa plate-like or “ruler” rod, as discussed above in section 1.1.1. Thetransversal stiffening rods 36 ₁-36 _(N) may have any other suitableshapes in other embodiments. Also, in this example, the layer oftransversal stiffening cables 63 ₁-63 _(T) is located between thetransversal stiffening rods 36 ₁-36 _(N) and the ground-engaging outerside 27 of the track 21. In other examples, the layer of transversalstiffening cables 63 ₁-63 _(T) may be located between the transversalstiffening rods 36 ₁-36 _(N) and the inner side 25 of the track 21.

In this case, the transversal stiffening rods 36 ₁-36 _(N) aredistributed in the track 21 such that there is one transversalstiffening rod 36 _(i) beneath every traction projection 58 _(i) of thetrack 21. In other words, a longitudinal spacing or pitch of thetransversal stiffening rods 36 ₁-36 _(N) may correspond to alongitudinal spacing or pitch of the traction projection 58 ₁-58 _(T).

In other cases, as shown in FIG. 32D, the transversal stiffening rods 36₁-36 _(N) may be distributed in the track 21 such that there is notransversal stiffening rod 36 _(i) beneath at least some of the tractionprojection 58 ₁-58 _(T) of the track 21. In such cases, the longitudinalspacing or pitch of the transversal stiffening rods 36 ₁-36 _(N) isgreater than the longitudinal spacing or pitch of the tractionprojection 58 ₁-58 _(T). For instance, in this embodiment, there is onetransversal stiffening rod 36 _(i) at every two of the tractionprojections 58 ₁-58 _(T). The longitudinal spacing or pitch of thetransversal stiffening rods 36 ₁-36 _(N) may be even greater in otherexamples (e.g., one transversal stiffening rod 36 _(i) at every three orfour of the traction projection 58 ₁-58 _(T)).

6. Carcass Periphery

In some embodiments, a periphery of the carcass 35, including its innersurface 32 and its ground-engaging outer surface 31, may be configuredto reduce noise generation and/or provide other benefits (e.g.,controlled rigidity). This can be achieved in various ways in variousembodiments, examples of which will be discussed.

6.1 Idler Wheel Path Projections on Carcass Outer Surface BetweenAdjacent Traction Projections

In some embodiments, as shown in FIGS. 33A and 33B, the ground-engagingouter surface 31 of the carcass 35 may define a plurality of idler wheelpath projections 64 ₁-64 _(P) which are located between adjacent ones ofthe traction projections 58 ₁-58 _(T) in the longitudinal direction ofthe track and which are aligned with respective ones of the idler wheelpaths 50 ₁-50 ₄ in the widthwise direction of the track 21 (i.e.,overlap with respective ones of the idler wheel paths 50 ₁-50 ₄ in thewidthwise direction of the track 21). The idler wheel path projections64 ₁-64 _(P) may help to reduce noise generation when they are crossedover by respective ones of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁,30 ₂.

For example, when a lower roller wheel 28 _(i) on a rolling path 50 _(i)arrives where an idler wheel rolling path projection 64 _(x) is located,the idler wheel rolling path projection 64 _(x) contacts the ground andcounters a tendency of the carcass 35 to deflect downwardly underloading of the lower roller wheel 28 _(i).

In this embodiment, each idler wheel rolling path projection 64 _(x) isuneven along the longitudinal direction of the track 21. Moreparticularly, in this case, the idler wheel rolling path projection 64_(x) is curved along the longitudinal direction of the track 21 so thatits thickness varies longitudinally.

The idler wheel path projections 64 ₁-64 _(P) may be configured invarious other ways in other embodiments. For example, in someembodiments, as shown in FIGS. 34A and 34B, each of the idler wheel pathprojections 64 ₁-64 _(P) may be generally flat along the longitudinaldirection of the track 21 and may occupy all of a longitudinal extentbetween adjacent ones of the traction projection 58 ₁-58 _(T) such thatthe idler wheel path projections 64 ₁-64 _(P) form “continuous” raisedlongitudinal bands 69 ₁-69 ₄ on the ground-engaging outer side 27 of thetrack 21.

6.2 Longitudinal Rigidifiers on Carcass Inner Surface and/or OuterSurface

In some embodiments, as shown in FIGS. 38 and 39, the inner surface 32and/or the ground-engaging outer surface 31 of the carcass 35 of theendless track 21 may comprise a plurality of longitudinal rigidifiers 70₁-70 _(R) for imparting longitudinal rigidity to the track 21. Each ofthe longitudinal rigidifiers 70 ₁-70 _(R) is an elastomeric formation,such as a projection or recess, formed in the rubber of the carcass 35that increases the longitudinal rigidity of the track 21 compared to ifthe track 21 lacked the longitudinal rigidifiers 70 ₁-70 _(R) but wasotherwise identical. The increased longitudinal rigidity of the track 21may help to reduce deflection of the track 21 when the idler wheels rollon the bottom run of the track 21.

In this embodiment, the longitudinal rigidifiers 70 ₁-70 _(R) arelongitudinally-rigidifying projections formed in the inner surface 32 ofthe track 32. More particularly, in this example of implementation, thelongitudinally-rigidifying projections 70 ₁-70 _(R) are shaped as raisedstrips that are generally parallel to the longitudinal direction of thetrack 21. The longitudinally-rigidifying projections 70 ₁-70 _(R) mayhave various other shapes (e.g., narrower ridges or ribs) and/or mayhave various other orientations (e.g., oblique) relative to thelongitudinal direction of the track 21 in other examples ofimplementation. In other embodiments, instead of being projections, thelongitudinal rigidifiers 70 ₁-70 _(R) may be longitudinally-rigidifyingrecesses (e.g., grooves that are generally parallel to the longitudinaldirection of the track 21). In yet other embodiments, the longitudinalrigidifiers 70 ₁-70 _(R) may include both longitudinally-rigidifyingprojections and longitudinally-rigidifying recesses.

The longitudinal rigidifiers 70 ₁-70 _(R) may be arranged in variousways. For example, in this embodiment, the longitudinal rigidifiers 70₂, 70 ₄ are located where the idler wheel paths 50 ₂, 50 ₃ are locatedwhile the longitudinal rigidifiers 70 ₁, 70 ₃, 70 ₅ are located outsideof the idler wheel paths 50 ₁-50 ₄.

Although in this embodiment the longitudinal rigidifiers 70 ₁-70 _(R)are located on the inner surface 32 of the carcass 35, in otherembodiments, similar longitudinal rigidifiers may be located on theground-engaging outer surface 31 of the track 21 in addition to orinstead of the longitudinal rigidifiers 70 ₁-70 _(R) on the innersurface 32.

6.3 Longitudinally Uneven Idler Wheel Path

In some embodiments, as shown in FIG. 35, an idler wheel path 50 _(i) onthe inner surface 32 of the carcass 35 may be uneven in the longitudinaldirection of the endless track 21. For example, in this embodiment, theidler wheel path 50 _(i) includes a series of idler wheel pathformations 67 ₁-67 _(F) distributed in the longitudinal direction of thetrack 21. The formations 67 ₁-67 _(F) constitute a deformableshock-absorbing zone in the idler wheel path 50 _(i) such that, whenidler wheels contact some of these formations 67 ₁-67 _(F), theformations 67 ₁-67 _(F) can deform to absorb the shock and thus reducenoise generation. In this case, the formations 67 ₁-67 _(F) includerecesses. In other cases, the formations 67 ₁-67 _(F) may includeprojections or a combination of recesses and projections. This is anexample of an embodiment in which a shock absorbency (i.e., a capacityto absorb shocks) of the track 21 at the widthwise position of the idlerwheel path 50 _(i) is greater than a shock absorbency of the track 21 ata widthwise position outside the idler wheel path 50 _(i).

A longitudinal spacing of adjacent ones of the idler wheel pathformations 67 ₁-67 _(F) may be selected so as to allow properdeformability for shock absorbance yet avoid creating unwantedvibrational effects as some of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30₁, 30 ₂ roll over these formations 67 ₁-67 _(F). For example, in someembodiments, the longitudinal spacing of adjacent ones of the idlerwheel path formations 67 ₁-67 _(F) may be no more than 5 mm, in somecases no more than 4, and in some cases no more than 3 mm. Thelongitudinal spacing of adjacent ones of the idler wheel path formations67 ₁-67 _(F) may have any other suitable value in other embodiments.

7. Track Elastomeric Material

In some embodiments, elastomeric material of the track 21 may havecertain characteristic which may help to reduce noise generation and/orprovide other benefits (e.g., controlled rigidity).

7.1 Fiber-Reinforced Elastomeric Material

In some embodiments, as shown in FIG. 44, the track 21 may be at leastmainly (i.e., entirely or mainly) made of fiber-reinforced elastomericmaterial which comprises an elastomeric matrix 87 in which are embeddedfibers 89 ₁-89 _(F). In other words, at least a bulk of the track 21 maybe made of the fiber-reinforced elastomeric material. In thisembodiment, the fibers 89 ₁-89 _(F) generally extend transversally tothe longitudinal direction of the track 21. This can provide transversalrigidity to the track 21.

In this embodiment, at least part of (i) the carcass 35, (ii) a tractionprojection 58 _(x), and (iii) a drive/guide lug 34 _(x) of the track 21are made of the fiber-reinforced elastomeric material. Moreparticularly, in this embodiment, at least a majority of (i) the carcass35, (ii) a traction projection 58 _(x), and (iii) a drive/guide lug 34_(x) of the track 21 are made of the fiber-reinforced elastomericmaterial. In this example, the track 21 is entirely made of thefiber-reinforced elastomeric material except for any reinforcement, suchas the transversal stiffening rods 36 ₁-36 _(N), the reinforcing cables37 ₁-37 _(M), or the reinforcing fabric 43, which may be embedded in thefiber-reinforced elastomeric material.

The elastomeric matrix 87 may include any suitable elastomer. In somecases, the elastomeric matrix 87 may include a single elastomer (e.g.,rubber). In other cases, the elastomeric matrix 87 may include two ormore constituent elastomers (e.g., two or more different rubbercompounds, one or more rubber compounds along with one or more othertypes of elastomer, etc.).

In this embodiment, each of the fibers 89 ₁-89 _(F) is a “short” fiber.For example, in some embodiments, each of the fibers 89 ₁-89 _(F) mayhave a length of no more than 10% of the width of the track 21, in somecases no more than 5% of the width of the track 21, in some cases nomore than 3% of the width of the track 21, and in some cases even less(e.g., no more than 2% of the width of the track 21). For instance, insome embodiments, the length of each of the fibers 89 ₁-89 _(F) may beno more than 30 mm, in some cases no more than 20 mm, in some cases nomore than 10 mm, and in some cases even less (e.g., no more than 5 mm).In this example of implementation, the fibers 89 ₁-89 _(F) are “chopped”or otherwise cut fibers.

In other embodiments, each of the fibers 89 ₁-89 _(F) may be a “long”fiber that extends along at least a majority of the width of the track21. For instance, in some cases, each of the fibers 89 ₁-89 _(F) mayextends along all of the width of the track.

The fibers 89 ₁-89 _(F) may be made of any suitable material. In thisembodiment, the fibers 89 ₁-89 _(F) are polymeric fibers. Morespecifically, in this example, the fibers 89 ₁-89 _(F) are aramid fibers(e.g., Kevlar fibers). Various other types of polymeric fibers may beused in other examples (e.g., polyvinyl alcohol (PVA) fibers). Also, inother embodiments, the fibers 89 ₁-89 _(F) may be any other suitabletype of fibers (e.g., metallic fibers, carbon fibers, glass fibers,etc.).

In some embodiments, as it may provide transversal rigidity and/or otherreinforcing effects, the fiber-reinforced elastomeric material of thetrack 21 may allow fewer or modified reinforcements to be embedded init. For example, in this embodiment, the transversal stiffening rods 36₁-36 _(N) have a high aspect ratio (e.g., are plate-like or “ruler”rods) and the track 21 is free of reinforcing fabric, as discussedpreviously.

The track 21 and its fiber-reinforced elastomeric material may beproduced using various techniques. For example, in some embodiments,sheets of fiber-reinforced elastomeric material, which includerespective portions of the elastomeric matrix 87 and respective ones ofthe fibers 89 ₁-89 _(F), may be produced by calendaring, extrusion,pultrusion or any other process in which those fibers are incorporatedinto that portion of the elastomeric matrix 87. These sheets may then beplaced into a mold for molding the track 21 such that the respectiveportions of the elastomeric matrix 87 and the respective ones of thefibers 89 ₁-89 _(F) of these sheets are combined into the track 21.Various other manufacturing processes may be used in other embodiments.

7.2 Slipper Elastomeric Material

In some embodiments, at least part of the elastomeric material of thetrack 21, including the elastomeric material 38 of the carcass 35, mayinclude “slipper” rubber 66. The slipper rubber 66 forms at least partof the inner surface 32 of the carcass 35 on which the slide rails 33 ₁,33 ₂ slide. The slipper rubber 66 exhibits a migration of lubricant(e.g., oil) contained within itself to the inner surface 32 of thecarcass 35 in use. This helps to reduce friction between the slide rails33 ₁, 33 ₂ and the track 21. As a result, this reduced friction mayallow a reduction in number of the slide clips 39 ₁-39 _(S) on the track21 or the track 21 to be free of slide clips altogether. By reducing oreliminating contact between the slide rails 33 ₁, 33 ₂ and slide clips,noise generation is reduced. Any suitable type of slipper rubber whichexhibits oil migration to its surface may be used.

7.3 Cellular Elastomeric Material

In some embodiments, at least part of the elastomeric material of thetrack 21, such as the elastomeric material 38 of the carcass 35, mayinclude cellular elastomeric material 71 (e.g., cellular rubber) at awidthwise position of an idler wheel path 50 _(i). The cellularelastomeric material 71 is elastomeric material which contains cells(e.g., bubbles) created by introducing a gas (e.g., air) or agas-producing agent (e.g., sodium bicarbonate) during manufacturing ofthe cellular elastomeric material 71. The cells of the cellularelastomeric material 71 may include closed cells and/or open cells. Thecellular elastomeric material 71 creates a deformable shock-absorbingzone in the idler wheel path 50 _(i) such that, when idler wheels rollover the cellular elastomeric material 71, the cellular elastomericmaterial 71 can deform more than if it was non-cellular (i.e., the sameelastomeric compound but without cells) to absorb the shock and thusreduce noise generation. Any suitable type of cellular elastomericmaterial which provides shock-absorption may be used. This is an exampleof an embodiment in which a shock absorbency (i.e., a capacity to absorbshocks) of the track 21 at the widthwise position of the idler wheelpath 50 _(i) is greater than a shock absorbency of the track 21 at awidthwise position outside the idler wheel path 50 _(i).

8. Track-Engaging Assembly

In some embodiments, the track-engaging assembly 24, including thewheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂ and the slide rails33 ₁, 33 ₂, may be configured to reduce noise generation and/or provideother benefits (e.g., enhanced load distribution). Examples of how thismay be achieved are discussed below.

8.1 Suspension Providing Increased Support

In some embodiments, the suspension unit 16 of the track-engagingassembly 24 may provide increased support. This can be achieved invarious ways.

8.1.1 Additional Idler Wheels

In some embodiments, as shown in FIG. 40, a number of idler wheels ofthe track-engaging assembly 24 that engage the bottom run 66 of theendless track 21 may be increased. For instance, in some embodiments,the track-engaging assembly 24 may comprise a set of idler wheels spacedapart in the longitudinal direction of the track system 14 andsubstantially aligned with one another to roll on a given idler wheelpath 50 _(i) on the bottom run 66 of the track 21 such that alongitudinal spacing V_(w) of any two successive idler wheels of the setof idler wheels on the idler wheel path 50 _(i) is less than half of thelength of the track system 14, in some cases no more than 40% of thelength of the track system 14, in some cases no more than 30% of thelength of the track system 14, in some cases no more than 20% of thelength of the track system 14, and in some cases even less (e.g., nomore than 10% of the length of the track system 14).

For example, in this embodiment, the track-engaging assembly 24comprises at least four idler wheels spaced apart in the longitudinaldirection of the track 21 and substantially aligned with one another soas to roll on a given idler wheel path 50 _(i) on the bottom run 66 ofthe track 21. In this case, there are six idler wheels rolling on thegiven idler wheel path 50 _(i). In other cases, there may be four, five,or more than six idler wheels rolling on the given idler wheel path 50_(i).

More particularly, in this embodiment, the track-engaging assembly 24comprises a set of six idler wheels 26 ₁, 28A₁-28A₅ rolling on theleftmost idler wheel path 50 ₁ and a set of six idler wheels 26 ₄,28A₆-28A₁₀ rolling on the rightmost idler wheel path 50 ₄. Also, in thisembodiment, the track-engaging assembly 24 comprises idler wheels 26 ₂,26 ₃, 28B₁-28B₄ which are located between the idler wheels 26 ₁,28A₁-28A₅ and the idler wheels 26 ₄, 28A₆-28A₁₀ in the widthwisedirection of the track 21 and roll on the idler wheel paths 50 ₂, 50 ₃.Various other wheel configurations are possible in other embodiments.

In this example of implementation, the idler wheels 26 ₁-26 ₄,28A₁-28A₁₂, 28B₁-28B₄ are mounted to elongated wheel-supporting members33A₁, 33A₂ of the track-engaging assembly 24. In this case, theelongated wheel-supporting members 33A₁, 33A₂ are not designed primarilyto slide on the track 21 like the slide rails 33 ₁, 33 ₂ discussed abovebut are rather designed primarily for supporting the idler wheels 26₁-26 ₄, 28A₁-28A₁₂, 28B₁-28B₂. In other cases, the elongatedwheel-supporting members 33A₁, 33A₂ may slide on the track 21 like theslide rails 33 ₁, 33 ₂ discussed above and thus may also constituteslide rails.

8.1.2 Additional Slide Rails

In some embodiments, as shown in FIG. 41, a number of slide rails of thetrack-engaging assembly 24 that slide along the bottom run 66 of theendless track 21 may be increased. For instance, in some embodiments,the track-engaging assembly 24 may comprises a plurality of side railsspaced apart in the widthwise direction of the track system 14 such thata widthwise spacing V_(r) of any two adjacent slide rails is less thanhalf of the width of the track system 14, in some cases no more than 40%of the width of the track system 14, in some cases no more than 30% ofthe width of the track system 14, in some cases no more than 20% of thewidth of the track system 14, and in some cases even less (e.g., no morethan 10% of the width of the track system 14).

For example, in this embodiment, the track-engaging assembly 24comprises at least three slide rails spaced apart in the widthwisedirection of the track 21. In this case, there are four slide rails. Inother cases, there may be three, five, or more than five slide rails.

More particularly, in this embodiment, the track-engaging assembly 24comprises four slide rails 33A₁-33A₄ which are evenly distributed in thewidthwise direction of the track 21. In this case, the slide rails33A₁-33A₄ are substantially identical in size and shape. Also, in thiscase, the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆ are mounted to respectiveones of the slide rails 33A₁-33A₄. Various other slide railconfigurations are possible in other embodiments (e.g., the slide rails33A₁-33A₄ may not be evenly distributed in the widthwise direction ofthe track 21; two or more of the slide rails 33A₁-33A₄ may differ insize and/or shape; one or more of the slide rails 33A₁-33A₄ may not haveany idler wheel mounted thereto).

8.2 Extremely Low-Friction Slide Rails

In some embodiments, the slide rails 33 ₁, 33 ₂ may include very lowfriction material to minimize as much as possible their friction withthe endless track 21.

In some cases, the slide rails 33 ₁, 33 ₂ may have a friction ofcoefficient with the endless track 21 that is low enough to allow thetrack 21 to be free of slide members (i.e., “clips”) such as the slidemembers 39 ₁-39 _(S) discussed previously without detrimentallyaffecting performance of the track system 14.

8.3 Track Tensioner

In some embodiments, as shown in FIG. 42, the track-engaging assembly 24may comprise a track tensioner 72 for maintaining tension of the endlesstrack 21. This may counter a tendency of the track 21 to stretch due tocentrifugal forces when it is driven at high speeds. In this embodiment,the track tensioner 72 is connected between a structural support 74 ofthe track-engaging assembly 24 and the rear idler wheels 26 ₁-26 ₄ tourge the rear idler wheels 26 ₁-26 ₄ in a direction to maintain thetension of the track 21.

The track tensioner 72 comprises a resilient device 73 configured tochange from a first configuration to a second configuration in responseto a load and return to the first configuration in response to removalof the load. More particularly, in this embodiment, the track tensioner72 is a fluidic tensioning system, e.g., a hydraulic or pneumatictensioning system, and the resilient device 73 is a piston-cylinderactuator connected to a fluid reservoir (not shown). In this example ofimplementation, the actuator 73 is a hydraulic piston-cylinder actuator.

In this embodiment, the piston-cylinder actuator 73 is connected to thestructural support 74 and to an idler wheel carrier 75 which carries anaxle of the rear idler wheels 26 ₁-26 ₄ and which can move in slots 76₁, 76 ₂ defined by the slide rails 33 ₁, 33 ₂. The tensioning actuator73 can apply the tension in the track 21 by extending or retracting tomove the idler wheel carrier 75 in the slots 76 ₁, 76 ₂ and thus moverear idler wheels 26 ₁-26 ₄ further or closer to the drive wheels 22 ₁,22 ₂.

The track tensioner 72 may be configured in various other ways in otherembodiments.

For example, in some embodiments, the resilient device 73 may comprise aspring such as a coil spring (e.g., a metallic or polymeric coilspring), an elastomeric spring or a leaf spring, or any other devicethat changes in configuration under load and recovers its initialconfiguration when the load is removed.

As another example, in other embodiments, the track tensioner 72 may belocated elsewhere and/or act on a different part of the track 21. Forinstance, FIG. 43 shows an embodiment in which the track tensioner 72comprises a first resilient device 91 ₁ contacting a first segment 92 ₁of the top run 65 of the track 21 which extends between the rear idlerwheels 26 ₁-26 ₄ and the upper roller wheels 30 ₁, 30 ₂ and a secondresilient device 91 ₂ contacting a second segment 92 ₂ of the top run 65of the track 21 which extends between the upper roller wheels 30 ₁, 30 ₂and the drive wheels 22 ₁, 22 ₂. In this embodiment, each resilientdevice 91 comprises a roller wheel 95 and a spring 93 that is connectedbetween the roller wheel 95 and a structural support 94 of thetrack-engaging assembly 24 in order to urge the roller wheel 95 againstthe track 21 to tension the track 21. This can help to counter atendency of the segments 92 ₁, 92 ₂ of the top run 65 of the track 21 todeform since they would otherwise be unsupported.

Instead of or in addition to using a track tensioner 72, in someembodiments, the endless track 21 may comprise a substantiallyinextensible material that can substantially prevent the track 21 fromstretching in a range of speeds at which it is expected to be driven.For example, in some embodiments, the reinforcing cables 37 ₁-37 _(M) ofthe track 21 may comprise Kevlar™ cables.

Although embodiments described above have been presented individually,any feature of any embodiment described above may be used in combinationwith any feature of any other embodiment described above.

While embodiments described above relate to a snowmobile, in otherembodiments, any feature of any embodiment described above may be usedin another type of off-road vehicle.

For example, in some embodiments, as shown in FIGS. 45A and 45B, anyfeature of any embodiment described above may be used in an all-terrainvehicle (ATV) 110 comprising a set of track systems 114 ₁-114 ₄providing traction to the ATV on the ground. The ATV 10 comprises aprime mover 112 in a driving relationship with the track systems 114₁-114 ₄ via the ATV's powertrain, a seat 118, and a user interface 120,which enable a user of the ATV 110 to ride the ATV 110 on the ground. Inthis case, the seat 118 is a straddle seat and the ATV 110 is usable bya single person such that the seat 118 accommodates only that persondriving the ATV 110. In other cases, the seat 118 may be another type ofseat, and/or the ATV 110 may be usable by two individuals, namely oneperson driving the ATV 110 and a passenger, such that the seat 118 mayaccommodate both of these individuals (e.g., behind one another orside-by-side) or the ATV 110 may comprise an additional seat for thepassenger. For example, in other embodiments, the ATV 110 may be aside-by-side ATV, sometimes referred to as a “utility terrain vehicle”or “UTV”. The user interface 120 comprises a steering device operated bythe user to control motion of the ATV 110 on the ground. In this case,the steering device comprises handlebars. In other cases, the steeringdevice may comprise a steering wheel or other type of steering element.Each of the front track systems 114 ₁, 114 ₂ is pivotable about asteering axis of the ATV 110 in response to input of the user at thehandlebars in order to steer the ATV 110 on the ground.

In this embodiment, with additional reference to FIGS. 46A and 46B, eachtrack system 114 _(i) is mounted in place of a ground-engaging wheel 113_(i) that may otherwise be mounted to the ATV 110 to propel the ATV 110on the ground. That is, the ATV 110 may be propelled on the ground byfour ground-engaging wheels 113 ₁-113 ₄ with tires instead of the tracksystems 114 ₁-114 ₄. Basically, in this embodiment, the track systems114 ₁-114 ₄ may be used to convert the ATV 110 from a wheeled vehicleinto a tracked vehicle, thereby enhancing its traction and floatation onthe ground.

Any feature described herein with respect to the track system 14 of thesnowmobile 10 may be applied to a track system 114 _(i) of the ATV 110.

The snowmobile 10 and the ATV 110 considered above are examples oftracked recreational vehicles. While they can be used for recreationalpurposes, such tracked recreational vehicles may also be used forutility purposes in some cases.

Certain additional elements that may be needed for operation of certainembodiments have not been described or illustrated as they are assumedto be within the purview of those of ordinary skill in the art.Moreover, certain embodiments may be free of, may lack and/or mayfunction without any element that is not specifically disclosed herein.

Although various embodiments and examples have been presented, this wasfor the purpose of describing, but not limiting, the invention. Variousmodifications and enhancements will become apparent to those of ordinaryskill in the art and are within the scope of the invention, which isdefined by the appended claims.

1.-22. (canceled)
 23. A track for traction of a vehicle, the track beingmountable around a track-engaging assembly that comprises a drive wheelfor driving the track and an idler wheel for contacting the track, thetrack comprising elastomeric material to be flexible around thetrack-engaging assembly, the track comprising: an inner surface forfacing the track-engaging assembly, the inner surface comprising anidler wheel path for the idler wheel; a ground-engaging outer surfacefor engaging the ground; a plurality of traction projections projectingfrom the ground-engaging outer surface; and a plurality of stiffeningrods extending transversally to a longitudinal direction of the track,each stiffening rod having a dimension in a thickness direction of thetrack that is less where the stiffening rod overlaps the idler wheelpath in a widthwise direction of the track than where the stiffening roddoes not overlap the idler wheel path in the widthwise direction of thetrack.
 24. The track of claim 23, wherein the idler wheel is a rollerwheel and the idler wheel path is a rolling path for the roller wheel toroll on a bottom run of the track.
 25. The track of claim 23, whereinthe idler wheel is a first idler wheel, the idler wheel path is a firstidler wheel path, the track-engaging assembly comprises a second idlerwheel spaced from the first idler wheel in a widthwise direction of thetrack-engaging assembly, the inner surface comprises a second idlerwheel path for the second idler wheel, the second idler wheel path isspaced from the first idler wheel in the widthwise direction of thetrack, and the dimension of the stiffening rod in the thicknessdirection of the track is less where the stiffening rod overlaps thesecond idler wheel path in the widthwise direction of the track thanwhere the stiffening rod does not overlap the second idler wheel path inthe widthwise direction of the track.
 26. The track of claim 23, whereina ratio of (i) a difference between the dimension of the stiffening rodin the thickness direction of the track where the stiffening rod doesnot overlap the idler wheel path in the widthwise direction of the trackand the dimension of the stiffening rod in the thickness direction ofthe track where the stiffening rod overlaps the idler wheel path in thewidthwise direction of the track over (ii) the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.1.
 27. The track of claim 23,wherein a ratio of (i) a difference between the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track and the dimension of the stiffening rod in thethickness direction of the track where the stiffening rod overlaps theidler wheel path in the widthwise direction of the track over (ii) thedimension of the stiffening rod in the thickness direction of the trackwhere the stiffening rod does not overlap the idler wheel path in thewidthwise direction of the track is at least 0.15.
 28. The track ofclaim 23, wherein a ratio of (i) a difference between the dimension ofthe stiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track and the dimension of the stiffening rod in thethickness direction of the track where the stiffening rod overlaps theidler wheel path in the widthwise direction of the track over (ii) thedimension of the stiffening rod in the thickness direction of the trackwhere the stiffening rod does not overlap the idler wheel path in thewidthwise direction of the track is at least 0.2.
 29. The track of claim23, wherein a difference between the dimension of the stiffening rod inthe thickness direction of the track where the stiffening rod does notoverlap the idler wheel path in the widthwise direction of the track andthe dimension of the stiffening rod in the thickness direction of thetrack where the stiffening rod overlaps the idler wheel path in thewidthwise direction of the track is at least 0.03 inches.
 30. The trackof claim 23, wherein a difference between the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track and the dimension of the stiffening rod in thethickness direction of the track where the stiffening rod overlaps theidler wheel path in the widthwise direction of the track is at least0.045 inches.
 31. The track of claim 23, wherein a difference betweenthe dimension of the stiffening rod in the thickness direction of thetrack where the stiffening rod does not overlap the idler wheel path inthe widthwise direction of the track and the dimension of the stiffeningrod in the thickness direction of the track where the stiffening rodoverlaps the idler wheel path in the widthwise direction of the track isat least 0.06 inches.
 32. The track of claim 23, wherein the stiffeningrod comprises a surface facing the inner surface and receding towardsthe ground-engaging outer surface where the stiffening rod overlaps theidler wheel path in the widthwise direction of the track.
 33. The trackof claim 25, wherein the stiffening rod comprises a surface facing theinner surface and receding towards the ground-engaging outer surfacewhere the stiffening rod overlaps the first idler wheel path in thewidthwise direction of the track and where the stiffening rod overlapsthe second idler wheel path in the widthwise direction of the track. 34.The track of claim 23, wherein the stiffening rod comprises a recessoverlapping the idler wheel path in the widthwise direction of thetrack.
 35. The track of claim 34, wherein a depth of the recess is atleast 0.03 inches.
 36. The track of claim 34, wherein a depth of therecess is at least 0.045 inches.
 37. The track of claim 34, wherein adepth of the recess is at least 0.06 inches.
 38. The track of claim 34,wherein a ratio of a depth of the recess over the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.1.
 39. The track of claim 34,wherein a ratio of a depth of the recess over the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.15.
 40. The track of claim 34,wherein a ratio of a depth of the recess over the dimension of thestiffening rod in the thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.2.
 41. The track of claim 23,wherein a longitudinal end portion of the stiffening rod overlaps theidler wheel path in the widthwise direction of the track.
 42. The trackof claim 25, wherein a first longitudinal end portion of the stiffeningrod overlaps the first idler wheel path in the widthwise direction ofthe track and a second longitudinal end portion of the stiffening rodoverlaps the second idler wheel path in the widthwise direction of thetrack.
 43. The track of claim 23, comprising a plurality of reinforcingcables extending generally in the longitudinal direction of the track.44. The track of claim 43, wherein the reinforcing cables are locatedbetween the stiffening rods and the inner surface in the thicknessdirection of the track.
 45. The track of claim 43, wherein thereinforcing cables are located between the stiffening rods and theground-engaging outer surface in the thickness direction of the track.46. The track of claim 23, comprising a plurality of drive/guideprojections projecting from the inner surface.
 47. The track of claim46, wherein the drive/guide projections are configured for engaging thedrive wheel to drive the track.
 48. The track of claim 23, wherein athickness of the track from the inner surface to the ground-engagingouter surface is no more than 0.25 inches.
 49. The track of claim 23,wherein the vehicle is a snowmobile and the track is a snowmobile track.50. A track for traction of a vehicle, the track being mountable arounda track-engaging assembly that comprises a drive wheel for driving thetrack and an idler wheel for contacting the track, the track comprisingelastomeric material to be flexible around the track-engaging assembly,the track comprising: an inner surface for facing the track-engagingassembly; a ground-engaging outer surface for engaging the ground; aplurality of traction projections projecting from the ground-engagingouter surface; and a plurality of stiffening rods extendingtransversally to a longitudinal direction of the track, each stiffeningrod being shaped such that a thickness of the elastomeric materialbetween the inner surface and a surface of the stiffening rod facing theinner surface varies in a widthwise direction of the track.
 51. Thetrack of claim 50, wherein: the inner surface comprises an idler wheelpath for the idler wheel; and the thickness of the elastomeric materialbetween the inner surface and the surface of the stiffening rod facingthe inner surface is greater where the stiffening rod overlaps the idlerwheel path in the widthwise direction of the track than where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track.
 52. The track of claim 51, wherein the idlerwheel is a roller wheel and the idler wheel path is a rolling path forthe roller wheel to roll on a bottom run of the track.
 53. The track ofclaim 51, wherein the idler wheel is a first idler wheel, the idlerwheel path is a first idler wheel path, the track-engaging assemblycomprises a second idler wheel spaced from the first idler wheel in awidthwise direction of the track-engaging assembly, the inner surfacecomprises a second idler wheel path for the second idler wheel, thesecond idler wheel path is spaced from the first idler wheel in thewidthwise direction of the track, and the thickness of the elastomericmaterial between the inner surface and the surface of the stiffening rodfacing the inner surface is greater where the stiffening rod overlapsthe second idler wheel path in the widthwise direction of the track thanwhere the stiffening rod does not overlap the second idler wheel path inthe widthwise direction of the track.
 54. The track of claim 51, whereina ratio of (i) a difference between the thickness of the elastomericmaterial between the inner surface and the surface of the stiffening rodfacing the inner surface where the stiffening rod overlaps the idlerwheel path in the widthwise direction of the track and the thickness ofthe elastomeric material between the inner surface and the surface ofthe stiffening rod facing the inner surface where the stiffening roddoes not overlap the idler wheel path in the widthwise direction of thetrack over (ii) a dimension of the stiffening rod in a thicknessdirection of the track where the stiffening rod does not overlap theidler wheel path in the widthwise direction of the track is at least0.1.
 55. The track of claim 51, wherein a ratio of (i) a differencebetween the thickness of the elastomeric material between the innersurface and the surface of the stiffening rod facing the inner surfacewhere the stiffening rod overlaps the idler wheel path in the widthwisedirection of the track and the thickness of the elastomeric materialbetween the inner surface and the surface of the stiffening rod facingthe inner surface where the stiffening rod does not overlap the idlerwheel path in the widthwise direction of the track over (ii) a dimensionof the stiffening rod in a thickness direction of the track where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.15.
 56. The track of claim 51,wherein a ratio of (i) a difference between the thickness of theelastomeric material between the inner surface and the surface of thestiffening rod facing the inner surface where the stiffening rodoverlaps the idler wheel path in the widthwise direction of the trackand the thickness of the elastomeric material between the inner surfaceand the surface of the stiffening rod facing the inner surface where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track over (ii) a dimension of the stiffening rod in athickness direction of the track where the stiffening rod does notoverlap the idler wheel path in the widthwise direction of the track isat least 0.2.
 57. The track of claim 51, wherein a difference betweenthe thickness of the elastomeric material between the inner surface andthe surface of the stiffening rod facing the inner surface where thestiffening rod overlaps the idler wheel path in the widthwise directionof the track and the thickness of the elastomeric material between theinner surface and the surface of the stiffening rod facing the innersurface where the stiffening rod does not overlap the idler wheel pathin the widthwise direction of the track is at least 0.03 inches.
 58. Thetrack of claim 51, wherein a difference between the thickness of theelastomeric material between the inner surface and the surface of thestiffening rod facing the inner surface where the stiffening rodoverlaps the idler wheel path in the widthwise direction of the trackand the thickness of the elastomeric material between the inner surfaceand the surface of the stiffening rod facing the inner surface where thestiffening rod does not overlap the idler wheel path in the widthwisedirection of the track is at least 0.045 inches.
 59. The track of claim51, wherein a difference between the thickness of the elastomericmaterial between the inner surface and the surface of the stiffening rodfacing the inner surface where the stiffening rod overlaps the idlerwheel path in the widthwise direction of the track and the thickness ofthe elastomeric material between the inner surface and the surface ofthe stiffening rod facing the inner surface where the stiffening roddoes not overlap the idler wheel path in the widthwise direction of thetrack is at least 0.06 inches.
 60. The track of claim 50, wherein thesurface of the stiffening rod facing the inner surface comprises arecess.
 61. The track of claim 60, wherein a depth of the recess is atleast 0.03 inches.
 62. The track of claim 60, wherein a depth of therecess is at least 0.045 inches.
 63. The track of claim 60, wherein adepth of the recess is at least 0.06 inches.
 64. The track of claim 60,wherein a ratio of a depth of the recess over a thickness of thestiffening rod in the thickness direction of the track is at least 0.1.65. The track of claim 60, wherein a ratio of a depth of the recess overa thickness of the stiffening rod in the thickness direction of thetrack is at least 0.15.
 66. The track of claim 60, wherein a ratio of adepth of the recess over a thickness of the stiffening rod in thethickness direction of the track is at least 0.2.
 67. The track of claim51, wherein a longitudinal end portion of the stiffening rod overlapsthe idler wheel path in the widthwise direction of the track.
 68. Thetrack of claim 53, wherein a first longitudinal end portion of thestiffening rod overlaps the first idler wheel path in the widthwisedirection of the track and a second longitudinal end portion of thestiffening rod overlaps the second idler wheel path in the widthwisedirection of the track.
 69. The track of claim 50, comprising aplurality of reinforcing cables extending generally in the longitudinaldirection of the track.
 70. The track of claim 69, wherein thereinforcing cables are located between the stiffening rods and the innersurface in a thickness direction of the track.
 71. The track of claim69, wherein the reinforcing cables are located between the stiffeningrods and the ground-engaging outer surface in a thickness direction ofthe track.
 72. The track of claim 50, comprising a plurality ofdrive/guide projections projecting from the inner surface.
 73. The trackof claim 72, wherein the drive/guide projections are configured forengaging the drive wheel to drive the track.
 74. The track of claim 50,wherein a thickness of the track from the inner surface to theground-engaging outer surface is no more than 0.25 inches.
 75. The trackof claim 50, wherein the vehicle is a snowmobile and the track is asnowmobile track.
 76. A track for traction of a vehicle, the track beingmountable around a track-engaging assembly that comprises a drive wheelfor driving the track and an idler wheel for contacting the track, thetrack comprising elastomeric material to be flexible around thetrack-engaging assembly, the track comprising: an inner surface forfacing the track-engaging assembly, the inner surface comprising anidler wheel path for the idler wheel; a ground-engaging outer surfacefor engaging the ground; and a plurality of traction projectionsprojecting from the ground-engaging outer surface; wherein a shockabsorbency of the track is greater where the idler wheel path is locatedin a widthwise direction of the track than where the idler wheel path isnot located in the widthwise direction of the track.